CPU: AMD FX9590 (8 core/4.7 GHz)
GPU: AMD TAHITI XT
In the new csgo batte royal mode, outside fps drops at 40 most of the time, all 3D engine settings set to minimal. In the other modes, fps is most of the time above 100 fps.
3D driver or game engine?
git of drm/llvm/mesa/linux(amd-staging-drm-next) no older than a week.
The actual main issue is while turning: since fps drops badly, it makes
turning all blury, then makes it quite harder to spot anything. And in "open
space" we turn all the time to check out if nobody is around (if you cannot
know you are alone in your tile). I run the 3d engine at 1920x1080, video
settings to minimal (native x11).
I did investigate the update speed of my mouse, because I was suspicious, and I
have above ~1000Hz update speed, using mouse-dpi-tool from libevdev.
You can increase significantly the performance issue while taking some height:
climb to the top of the "water station", turn to look anywhere, the fps drops
below 30fps. Seems to be significantly linked to the 3d engine performance.
I suspect it could be your system showing its age. It seems common that users on Windows also reported FPS drops with Danger Zone. You could try some of the generic (non windows) suggestions found here  to reduce CPU use etc. Otherwise it might be upgrade time.
it does not seem to be the driver, but the 3D engine: I get the same low FPS while lowering the GPU settings. Seems to be a 3D meshes LOD computation performance issue in open areas with far sight.
csgo source1 engine seems enough for classic gameplay csgo maps, but quite bad for danger zone gameplay maps (expected).
apex legend 3D engine is actually a heavily modified source1 engine (and there are probably map specific optimizations).
I did try the config community mod showed in the video, did not help.
It is said csgo is being upgraded to source2 then vulkan: let's wait and see.