After some research it seems AMD has still some issues with encode quality, idle power consumption and possibly drivers and support in Unraid, with the stock kernel.
Thinking about going with a combination of Intel Xeon E-2468 and Intel Arc A380 instead.
Encode performance has been a mixed bag on AMD, you need to crank up the bit rate to get on par vs QuickSync esp for a TV DVR box as sports ball leads to heavy motion blur.
Yes, with the same memory modules and motherboard BIOS version Multibit ECC works with the 7800X3D as expected:
Also nice that error injection works, that makes it easier to practically test if ECC works correctly, on AM4 I never saw this feature working. On AM4 the most reliable way to check if ECC is functioning correctly is overclocking the ECC memory to its limit without increasing the memory voltage to force memory errors which then get corrected and this action is subsequently logged in the memory testing program.
Stuff that also just works after swapping the 8700G out for a 7800X3D:
Still sucks that on AM5 ASUS seems to be the only reliable option left regarding ECC memory support, ASRock manufacturs many of its motherboards with the necessary additional traces for the memory modules but then messes up the BIOSes regularly 
On AM4 ASRock, Gigabyte as well as ASUS made motherboards with ECC generally working, only MSI was the negative exception.
As mentioned earlier the 8700G gets returned, feel a bit dirty… but on the motherboard I have which functions completely fine including prime95 with AVX-512 with the 7800X3D it is actually unusable in Windows with the 8700G, not even thinking about ECC, PCIe Bifurcation or IOMMU options.
Hopefullly by the time the PRO 8750G or whatever it is going to be called is going to be released, BIOS and driver updates will have improved the situation.
Tested AM4 APUs pretty early after their initial releases (3200G, 4750G and 5750G) and the situation there was never this bad.
Since the return window closed I am now again without the 8700G and will revisit this thread as soon as I get my hands on a PRO 8700G/8750G.
If anyone has an 8700G feel free to post your experiences with newer BIOS versions and your motherboard of choice here, I couldn’t test the latest BIOS 1905 from ASUS that disabled the on a desktop useless STAPM feature, maybe there are already other bug fixes in that release that aren’t explicitly mentioned.
Shouldn’t be that long until the PRO APUs like the Ryzen PRO 8700G are going to show up.
