X11 mostly gives better gaming performance, specially on nvidia GPU’s. Probably your hardware utilise better on X11 as on Wayland and when your hardware is overheating the crash cascade then even stronger.
Are you aware that we also have the magic system hotkeys? As long you get have a Kernel Crash, you can revive your system, or at least you can initiate a clean shutdown.
For investigating closer around your problem, you might want to temporary disable your i-gpu in your Bios to find the culprit… its not always a easy task to find a solution.
You can also try out different Kernels 6.18 LTS for example.
Did you created this system info, while your game was running?
I ask this because for idle CPU temps, 66 degree is really hot.