I know this is an old post, but I had a similar issue on zombies with a 2080 Super. Changed the settings, and followed the low FPS fix but that didn't work. I play on a wireless xbox controller and as soon as I switched to keyboard and mouse (mid-game, controller still connected to the pc) the fps went back to normal, 200+ frames. The issue seemed to be the bluetooth xbox one controller, I disconnected the controller in bluetooth, plugged it in via usb and had no fps issues since.
Wzythom
@Wzythom