Thanks for the help! Smoothed things out a bit, but Call of the Dead is still unplayable. But it's definitely because of the wild FPS swings I get on the map. Seems like it's related to where I'm looking. From spawn, looking towards where jug is, my FPS drops to 20 or lower sometimes. Doesn't affect walking speed, or anything really when using a controller. But mouse and keyboard are borked.
Maybe someday the performance of that map will be fixed. I tried a few proton versions without any improvements. For now, I'll just use a controller. A bit annoying that the PC version has no aim assist for controller...
Basically seeing the same issue as this thread
I've also enjoyed CalyxOS on my pixel