this is why its a good practice to just separate different series of gpus, less hassle in the end. the masses of people like yourself just don't learn
I have in one rig a mix of amd cards : rx vega + 2 rx 570 + 3 rx 480, some of them even with different size of memory and all is working as intended.
I've flashed rx64's bios into my vega, then flashed all rx to modded bios, install blockchain drivers, patched it, disabled in registry crossfire, restart.
all is working right form the start..