It is possible that he is not hitting direct scanout and some of the perf hit is from that. If you launch gamescope as the compositor (i.e., not nested) he should get better performance since direct scanout should happen. It is also possible that some overlay is causing compositing to occur that is killing perf. In general, I don’t think there is anything CachyOS related (beside x86-64-v3/4 optimized kernel and packages) that is going to help here.