Not sure about ASRock, but I have (2) Sapphire 6900 XTs that both work in their own Razer Core X enclosures:
Both were plug and play out of box within Monterey and now Ventura. Only addon was (2x) splitters (https://www.amazon.com/gp/product/B072JR4H3N/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) since the PSU cables the enclosure arrived with were short on pins.
Check out egpu.io for any builds with ASRocks? From what I can tell with other GPU(s) such as the 6600 XT and RX Vega 64, all of them have worked for me in both OS's.
Two. How can I safely power my risers?
Youre going to end up doing almost exactly what I did for 5x Vegas
I’d go with those risers, they’re what I used and are working flawlessly. To power them, you can use the 6 pin to SATA cables. You’d only need to take up two of your SATA ports on your main PSU for the risers, then you’d need the Molex to 6 pin for the Add2PSU. That would use up all of your SATA ports on your main PSU. The molex will otherwise be useless unless you’re going to power more fans with them.
I am powering two Vegas with my main PSU and 3 with my slave PSU, and I’m also powering my SSD with the slave. https://i.imgur.com/wPPd0YB.jpg
There’s a pic of my rig but it’s not the best lighting.
If you have those fancy cords that are 8 pin to 2x 6+2 then you can ignore the next paragraph. I only have one of those and it made life so easy but I was unable to find more
Your biggest problem is going to be running out of 8 pin to 6+2 cords, or running out of 8 pin VGA ports on your PSU’s. My gigabyte and XFX Vegas came with y splitters that made it so each card only took up one slot on the PSU but required two PCIe cords to plug into the y splitter and then the card. these may help you
