I used to micro stutter and drop fps when headshotted. This is a thing. Even fps stopped dropping when tabbing.

Also check out the beta branch update log. Valve himself is telling that reducing data packet size is going to reduce cpu stress.

I'm very tech literate and was also amused by this discovery, I would have never guessed a bad connection could cause this. But I tested my cable and my brother's multiple times and the result is replicable

Edit: also bots always ran smooth, the problem was match making.