Vaccaria

What I don't understand is when a person tries to point out in words something that only they are experiencing. I've done some tests of what you pointed out. I got a match.
I also know the reasons for the CPI inconsistency on the mouse, i.e. lack of consistency.
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

4.17*100=417 px
The cursor started and ended the movement of the active are - That means the math works.
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
You want to know how many pixels you can get through at 216 mm.
so:
216/25.4=8.50393700787*800=6803.1496063 px - We multiplied the distance by CPI, we got a value, let's understand it as px. Since CPI are counts, they can be tied to anything, in the case of a monitor, they are tied to resolution, i.e. px.
>>>
6803.1496063/1920=3.54330708661 - We found how many can fit 1920 px on this area.

///
1800 dpi
sensitivity "0.568889" zoom_sensitivity_ratio_mouse "1.000000" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.000000" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.000000" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.000000" (Zoomed 2: AWP) or zoom_sensitivity_ratio_mouse "1.088317" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.096285" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.124343" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.127085" (Zoomed 2: AWP) ///
1600 dpi
sensitivity "0.755628" zoom_sensitivity_ratio_mouse "1.088317" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.096286" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.124343" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.127085" (Zoomed 2: AWP) ///
1600 dpi
sensitivity "0.853333" zoom_sensitivity_ratio_mouse "0.963707" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "0.970763" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "0.995608" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "0.998036" (Zoomed 2: AWP) or zoom_sensitivity_ratio_mouse "1.088317" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.096285" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.124343" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.127085" (Zoomed 2: AWP) ///
1355 dpi
sensitivity "0.755628" zoom_sensitivity_ratio_mouse "1.088317" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.096286" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.124343" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.127085" (Zoomed 2: AWP) ///
1200 dpi
sensitivity "0.853333" zoom_sensitivity_ratio_mouse "0.963707" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "0.970763" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "0.995608" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "0.998036" (Zoomed 2: AWP) or zoom_sensitivity_ratio_mouse "1.088317" (Zoomed: AUG, SG 553) zoom_sensitivity_ratio_mouse "1.096285" (Zoomed 1: AWP, SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.124343" (Zoomed 2: SSG 08, G3SG1, SCAR-20) zoom_sensitivity_ratio_mouse "1.127085" (Zoomed 2: AWP) ///
I have no idea which option is right for you.
You can't get rid of the slowness of character movement at 16.9. You can only change Pixel ratio(mp and dpi)(res).
 
 
 

Osu vs McOsu and the impact on conversion from Hipfire to ADS, Scope.
At the very beginning of the study, I used native osu. McOsu I used as 3D, with a native square osu.
Since I used native osu, the area of note appearance has a square. By moving the pointer over the square area each time, I arrived at the method: MDH 60% from Hipfire to ADS, Scope.
When I moved to McOsu to test the full screen format instead of the square, I continued to use MDH 60%.
I didn't even have any doubt that MDH 60% was the most effective.
Not long ago I came across questions, topics, discussions about 100%MDH, and it prompted me to double-check this method, because past experience is past experience, because as soon as you think, there is, found - you start to die.
///
When I started running tests with MDH 100%, my confidence was shaken, I immediately realized what was wrong. Square is MDH 60%, but when fullscreen it is MDH 100%.
From here we get the following data:
1) Native osu is 0-60%, maybe someone will have 100%, but according to my data 60% is most effective.
2) Fullscreen McOsu is 60-100%, yes, can use 60%, 90%, 98.434389% or any other value to address any shortcomings you may personally have. But for the sake of understanding, let's take 100% as a base.
How to make full screen mode:
Need 3 commands, I don't know how these values will display on other monitors, my values are as follows:

osu_playfield_stretch_x 0.5
osu_playfield_border_bottom_percent 0.112
osu_playfield_border_top_percent 0.112

1) Manually enter one command each time you run McOsu. The key combination to open cmd is "Shift+F1"
or 
2) Enter these lines in the file "osu.cfg" in the path "*\SteamLibrary\steamapps\common\McOsu\cfg"
///
The images show the value of the size of the circles(cs 0). The higher the cs, the more the area is narrowed. This is the mechanics of cs, there is no way around it. Therefore, at the usual values of 4-6 cs, the area will be narrowed.
Comparison of area:
Native area in osu(cs 0)

Fullscreen(cs 0)

What does cs 4 look like with fullscreen.

Or
Here are more fullscreen for specific cs values:
cs 2
osu_playfield_stretch_x 0.471
osu_playfield_border_bottom_percent 0.097
osu_playfield_border_top_percent 0.097
cs 4
osu_playfield_stretch_x 0.446
osu_playfield_border_bottom_percent 0.081
osu_playfield_border_top_percent 0.081
cs 5
osu_playfield_stretch_x 0.432
osu_playfield_border_bottom_percent 0.073
osu_playfield_border_top_percent 0.073
cs 6
osu_playfield_stretch_x 0.418
osu_playfield_border_bottom_percent 0.064
osu_playfield_border_top_percent 0.063
I check the values in photoshop to make sure the lines are the same from the edges.
///
Well, another confirmation that the same method shows different effectiveness when the environment changes. This means that you should choose methods by studying your own environment of training, playing games or whatever else you do with your PC:)
Let's take The Finals game as an example, the calculator shows limit of MDV 100%, i.e. in the game cannot be set higher than this value. The environment limits by imposing restrictions.
Playing native osu, you will be changed by the osu environment as there is no way to change the area.
///
That's all for now.
 
Tag solution
On topic, this is:
Click
Click together with Click
Click
other posts additional information

Yes, these methods do not assume the same cm\360.

"Truly what is the best sensitivity for each individual and what is the way to find it??"- Does that ever happen in our lives?
Try to understand: there is no sensitivity that suits you and only you, just as there is no setting that suits you and only you. Sensitivity and settings are not out there waiting for you to find them. 
And now I'll use my own example to describe why I wrote it that way. Everyone likes to ask questions and read the answers, based on the experience of another (this is exactly what you asked) Here you are on the path as other gamers to find sensitivity, who has not been on it, even me. You want to find one, and only for you, so you don't have to spend time on training and searching (no need to search for anything, take any settings and train, provided that your monitor, system unit and peripherals are not very different in characteristics, otherwise there may be problems "just for you", because of these settings: "No point in 120Hfov on a square monitor", hint get it)
I've been testing a lot of different settings (fov, sens, etc.) and here I realized what difference it makes what settings if the result is directly tied to training. Settings of everything under you are called - I have a habit, which has developed over many years(muscle memory) and I want to get closer to the habit, so there are different settings for this, but when you are "0" settings will not give anything 0*100=0.
If you have a fixed distance of a centimeter (how much is it) it does not say anything, because in the game there is still FOV, you'll always look in the center (where the sight) and occasionally look at the monitor away from the sight (left-up, right-up, etc.) You will always feel sens on 2D, and play in 3D. What is it? If you play a game where there is a recoil pattern in the weapon, you won't control it with 180/90 degree turns, will you? You will control it in a 2D monitor because you have a monitor in front of you and it's flat. All the talk about sensitivity conversion refers to 2D. People are discussing their habits.
I was testing any centimeter at 360, eventually I got written about acceleration and went to study acceleration and for months now all I needed was acceleration, it is able to close any need and craving for SENS changes(Everyone likes to change the multiplier in games(no sense but they do it)
All you need to do is not seek approval from other people. You have your own head on your shoulders, and it is able to examine everything around you and create the necessary conditions for you in the game.

I don't know how windows scaling works for games, but the principle as you described, if we take 1920x1080 and we have 400dpi, if we put 720 and stretch it, 400dpi x2 get 800. If we don't stretch 720 in the game and play in the black bars, the 400 dpi will stay the same on the monitor, that is, there will be no increase.
As for the multiplier in the game and dpi, the shooting is on a 2D monitor and the movement is on a sphere. There is a fixed distance of 360 and people write about it as "sens" in the game.
Let's say we have 20 cm, and these 20 we will feel on a 2D monitor at different FoV 120 and 60 in WZ, at 60 sharp and at 120 inert.
You can also measure the path in monitors and pixels:
360\120=3*1920=5760 total path in pixels
360\60=6*1920=11520 total path in pixels
S=c(monitors); t=l;

When the angle of view changes, the speed of the pointer changes, the path does not change, the path is a circle 360=20cm. When the viewing angle is 60, to cover the distance, you need to spend from edge to edge 6 monitors, but you need to match the path of 20cm on the mouse pad. At 120 it is already 3 monitors, and since the monitors are physically the same - one characteristic in length, in order to traverse a circle of 360 degrees around its axis, the cursor must move slower. Therefore, when setting FoV 120, there is a fisheye effect and the cursor becomes inert. If you set it to 60, the cursor will be very sharp, despite the fact that the character will move as if slowly, it will be difficult to aim. 120 the character will be fast, but the cursor will be inert (slow). This is all related to the multiplier "a", it starts to appear and affects the fact that the equality is fulfilled. Multiplier "a" depends on viewing angle, speed (speed depends on viewing angle, but in general they are complex)

c,l are length units (cm, m, inches, pixels, etc.)
C(the length of the circle in the game)=a(the product of some multiplier)*l(the length traveled by the mouse on the mouse pad). The a1 multiplier depends on the viewing angle(60), on the pointer movement speed, on the sensitivity in the game, not on dpi, sens. - is the speed of the pointer movement.
The "c, l" of the path depends on dpi. The speed of movement depends on "sens. 

let's hypothetically imagine that the path of the mouse from edge to edge on the mouse pad equals one monitor. For the equality 6=a60*1(figuratively, these numbers(6;1;) are not values, they include a complex of numbers) and 3=a120*1 for this equality to hold, a60≠a120. That is, the multipliers "a" are not equal, that with different viewing angle, different dependence of "v" speed, different dependence of "sens." sensitivity, we can call them synonymous v=sensitivity, sensitivity=v.