I lose fps when focusing the game

[nikkmann]

Had this exact issue, try disabling geforce overlay if you haven’t

GeForce Overlay Causing Massive Instability/FPS Loss. Thoroughly Tested

I’ve been far less thorough than you, but it does seem like this helped me. RTX 3080, 5900x, 32 GB RAM, some SSD that I don’t exactly remember the info on right now, B550 AORUS Mobo. I’ve definitely also seen other games where GeForce Overlay is the culprit in various bad behavior.