SNOYS0915

Low sens is for people who want instant results. The lower they go, the less they can potentially do. The sens ends up defining them as it prevents them playing certain games, certain roles, certain weapons, etc.
You also got to factor in hardware and peripheral choice, physical strain, RSI, energy requirements, sensitivity spread, etc.
Light mice and large mouse pads become a necessity. Muscles start to accumulate fatigue and stress due to no downtime in excessive movement. Playtime may decrease because one requires more energy to feel like playing. The holding of the mouse and style of motion stays the same past a certain point, making any sensitivity slower than that point a possibility. This causes a constant change of sensitivity, within a pretty large spread. Things like that.
Stick with a comfortable sens that you feel can accomplish anything given enough time practicing with it. With 4 years as a time frame, I wouldn't even consider falling into the low sens trap.

I'm actually not sure, but if I recall correctly I read somewhere that some of the pros have very different sensitivity in different games.

Most pros, and streamers for that matter, seem to choose a sensitivity based on what feels right or what they feel works for that type of game. Take shroud for example, his PUBG (30cm) and Blackout (35cm) sensitivies are a lot faster than what he uses in CS (47cm) just because he's found that it works best for him.
Anyways, it can be fun to compare sensitivities with pros but in the end I think everyone will agree that it's best to find that perfect sensitivity on your own. 

Transfer from CSGO every time.

I edited you post format for clarity.
Just select CSGO as the first game and enter all your details (sensitivity, resolution, DPI), then select BO3 or R6 and set the correct FOV.
That's basically all you need to do unless you have some spesial settings.
The output will show you the correct sensitivity.