Hello tryhard, and to everyone else confused about their fps problem! Here is a solution that might solve it.
The coloured outline on your teammates is most likely what's causing the low frame rates and here's the command to remove it: "glow_outline_effect_enable 0". Type that command in the console and it should increase your fps, I can't guarantee it goes back to normal but it sure as hell lowers the lag (in my case it increased my fps x3)
Hope this helps