Ok, this is weird. I had previously tried out the "newest" (as of, a month or so ago?) BIOS/UEFI for my AB350M Pro4 board, in this rig with a Ryzen 1600, and I had nearly endless crashes, failures to boot Windows 10, it was a total mess.
I had to clear CMOS, and somehow got back into the BIOS menu, to re-flash back to 3.40.
Well, fast-forward to tonight, and I flashed from 3.40, to 4.50 (not sure if that's what I tried before), and this time, it seems like it "took" OK. I let it reboot itself a few times afterwards, and then it booted into Windows 10, no problem thus far, and mining away.
Shrug. WFM this time, now.
I guess I can then drop in a Raven Ridge?
Edit: It might have been 4.40 that caused me all the trouble, that version seems to have been pulled.
Edit: UEFI 4.50, lets me use my Team Vulcan DDR4-3000 16GB kit @ 2933 just by setting XMP!