Grammer Nazi in me is going crazy... must... not......
Back to the question.
It sort of has to do with your mentality and comforts. Sniping definitely requires precision of your mouse movements especially if you drag shoot. A very high dpi or sensitivity will sacrifice mouse precision for mouse speed, and vice versa. Setting will only take you as far as it can. The rest is always practice/repetition.
Also disable mouse pointer precision/mouth smoothing/mouse acceleration. When you move your mouse X amount of centimeters, you should be turning Y amount of degrees. Enabling those things will make your play inconsistent. (Move X centimeters => Y + some speed factor, etc.) Disable pointer precision in Windows mouse settings, and mouse smoothing in game options.