I think I found the issue after searching for 5800x WHEA_UNRECOVERABLE_ERROR:
Disabling CPB and PBO in the BIOS fixed my stability problems.
I was chasing the wrong tail because on my 3700x build changing those memory timings seemed to work.
Might be too early to say. Previously games were crashing within about 2 minutes of being launched. Played for 20 minutes without a crash this time.
