First of all, I'm an player from Taiwan, I often use the mouse sensitivity to find the right edpi.
My English is not very good so I basically use translations or simple pictures.
Changing the aspect ratio in most games increases the HFOV, but a few games decrease the VFOV.
In picture 1, suppose there are two games with the aspect ratio set to 1:1, and the viewing angles are the same, then when the aspect ratio is changed to 16:9,
game(A)
VFOV:58.715507
HFOVE:90
and
game(B)
VFOV:90
HFOV:121.284493
Actually, the size of the objects in the frame has not changed, so their sensitivity should be the same.
We change the sensitivity by changing the FOV, but because of the different ways of changing the picture due to the aspect ratio, the sensitivity of different FOVs should be the same.
I don't know if my thinking is correct, but maybe this can help in finding a better method for sensitivity conversion.