Ubuntu 21.04 - X.Org vs. Wayland Linux Gaming Performance
For most games the performance is quite comparable between the X.Org and Wayland session with the games going through XWayland. Years ago there were often performance penalties but at least for the current state of GNOME's Mutter compositor, it's generally at par these days to the X.Org performance.
One of the exceptions was Civilization VI running slower on Wayland than X.Org. However, this is also one of the few games stuck to running in windowed mode due to issues introduced with recent updates to the game when benchmarking.
In a majority of the native Linux games as well as Steam Play titles, the GNOME Wayland session with Ubuntu 21.04 on the open-source Radeon graphics was working out well with no major difference in performance.