I also have i9-12900K and official Qubes 4.1 release ISO didn’t work for me when I’ve tried to install in UEFI mode.
But latest Quebs ISO build with kernel-latest worked fine.
Can you check your CPU frequency scaling?
I had an issue with it and wanted to know if others have the same problem:
First run this command in dom0 to see your current governor and if turbo mode is enabled:
xenpm get-cpufreq-para
Check in dom0 your cores frequency in idle mode:
xenpm start 1|grep "Avg freq"
Then assign 16 vcpus (or 24 vcpus if you enabled smt) to one of your VMs and start it. Run some high load process there, for example 7z benchmark:
7z b
Check in dom0 your cores frequency:
xenpm start 1|grep "Avg freq"