sorry if my english is bad.
i use 20-60cm sensitivity for different games,and i've play CSGO for 1000+ hours.
Here's my points:Low sensitivity doesn't force you to aim without finger.40cm sensitivity is low enough that you can aim with only your arms,but aiming with fingers and wrists at a short distance may be more accurate than arms.
CSGO Pro Scream seems to aim with fingertip grip at 40+cm sensitivity, I'm not exactly sure.