Thank you all for your time and response.
My riser(VER 009) has a 6 pin connector. I have used one sata line to power one riser. So 4 individual Sata lines powers 4 risers. But have to use a 'SATA to 6 pin converter' cable which is of 18AWG, 300V, 80deg C. Runs fine with no heat at the connect junctions. One GPU is placed on the mobo itself.
I have 5 PCIE cables running from the PSU. Each PCIE cable has 2 x 8 pin connectors. So after connecting 5 GPUs, I still have 5 PCIE connectors freely hanging. I believe that these 5 PCIE connectors can be used to power the risers.
TDP of RX580 is 185W
TDP of 1070 is 150W
TDP of 1060 is 120W
TDP of 1660ti is 120W
I have 7 1660 super, 1x3060 and 1x3060ti connected to an RM1000x, I recommend using molex risers and if you need to use SATA I recommend it only for low consumption cards like the 1660 but still only one riser per cable.
Can you please explain how did you manage the cables to connect 9 GPUs along with the risers to the PSU.