On the ASRock H110 Pro BTC+ I use an EVGA 1600 W T2 (9 PCI-E ports) for the motherboard, all the risers and 4 RX 580s's together with a 1000 W P2 (6 PCI-E ports) and 850 W G2 (4 PCI-E ports) for the rest of the cards. I connect two 6-pin risers to the 1600 W T2 on each PCI-E cable, or 3 if it has a pigtail. I connect one GPU per PCI-E cable using the the 8-pin + 6-pin pigtail cables or with an 8-pin to 6+2 splitter cable.

https://www.aliexpress.com/item/20CM-Black-Sleeved-8-Pin-PCI-E-GPU-to-Dual-8-6-2-Pin-Splitter-PC/32688175733.html?

You can also use dual molex to 6-pin PCI-E adapter cables to connect the risers (two risers per SATA/Molex cable max).

https://www.aliexpress.com/item/3pcs-Molex-4pin-ide-to-6-Pin-PCI-Express-Video-Card-Pci-e-ATX-PSU-Power/32827796670.html?

https://www.aliexpress.com/item/PCI-E-Adapter-Cable-Dual-15-Pin-SATA-Power-To-6-Pin-PCI-E-PCI-Express/32837874103.html?