I wouldn't mess around too much with sensitivity, just pick something that feels comfortable that allows you to block or shoot targets accurately. Everything else is just muscle memory by doing the same movements over and over with the same sensitivity
Depends how you hold the mouse too. If your hand stays in the same position and you aim with wrist/fingers then you probably want higher sensitivity than someone who palms the mouse and moves the whole thing with the arm
I use about 15-20cm to turn 360 degrees and aim without moving the arm. Its a bit left of the middle in options and 800 dpi
Do recommend not to fiddle too much though, it all takes second place to simply getting used to one sensitivity and using something thats comfortable