Well, it gets hot quickly under load (I only opened a picture previewer), see the attached screenshot.
For sure, many thanks for the solution! I'm having Issues with Quicksync with this setup. I Managed to make it work right but suddenly I cannot longer open Final Cut... And nothing has changed. Guess is Lilu+Whatevergreen managing things...The extent of my dealings with ASUS support made it pretty clear that once in this new BIOS, it is impossible to downgrade. Maybe they will fix this in a future BIOS update. I don't know why you'd need to downgrade anyway since with this fix this BIOS works perfectly.
I was able to downgrade my ASRock Z390's system's BIOS from version 4.0 to 1.2 by using the windows BIOS update mechanism. I did not expect it to work because ASRock warn you you cannot downgrade and because the processors microcode was upgraded with BIOS 4.0 I did not have much hope for it but as I bought my board specifically for a Hackintosh, I tried it anyway. Once I got back to BIOS version 1.2 everything worked again with no other changes.ASUS Rog Strix Z390-i didn't have that option in the latest bios though. Search showed "RTC wake schedule" or something. So the solution wasn't for all motherboards. That's when I got frustrated and gave up. I know people are using hackintoshes on those boards so it can be fixed. I just don't know how. It was pretty board!