Let me address the bios flashing...you just can't do it.
I know for a fact flashing any type of modded bios on the Ryzen motherboards is not an easy feat and requires a UEFI boot disk with powershell and a ton of switches plus 2 different flashing programs one written for just this purpose over at overclock net. Also the USB stick has to be created a certain way via UEFI boot for any of this to work.
Afuefix64 name_bios.cap /P /B /N /K /X /CLRCFG
(this action we clean all parameters from old bios and update the bios itself and is require otherwise it will fail to program everything correctly)
Then you have to flash Afugan name_bios_mod.rom /GAN
With all this said, you cannot modify the .cap bios and flash it by any means. And no the old flashback methods just do not work either where we could do that on 990FX motherboards. We just do not have all the crypto keys you must have and bios signing abilities.
I have cross flashed my C6H Wifi to the update C6H 6001 official bios and then the modded to show hidden bios options. There is no other way to accomplish this bios flash without doing these steps. So there.
Also the PSP chip cannot be updated other then bios flashing..unlike the MEI on Intel.
Full disclosure I have both a Ryzen 1700X system and Intel Skylake 6600k system as well as my older 990FX system.