I just checked and realised I’m on 6.16 as well. I don’t think the xanmod kernel will solve your problem, it could be worth a try though, if you are desperate.

I have/had the same problem in cs2 (native; so no proton involved) and AMD RX5600XT.

My performance degradation is seemingly fixed for now after my last system update (and switch to latest xanmod kernel (which is at 6.12 I think))

I have an 5600xt and i used to have crashes quite regularly. Disabling hardware accel in firefox helped. Now i only have crashes when playing games from heroic.

Unfortnately all those crashes turned some friends away from linux

You are supposed to use --mangoapp instead of mangohud see gamescope --help