Our C-Series 12VHPWR would be compatible as well, we have a 3x8 on Amazon if you would like it quick without waiting. These have prime. :)
You can go with our 12VHPWR 2x8 or 3x8 options for your GPU. You can do direct replacement cables if you want those instead of extensions though.
Our direct replacement option can be found on Amazon as well if you want something speedy on shipping that would plug directly into your PSU. You can find that here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
For the RM850x you would want this kit here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ2BB9JZ?ref_=ast_sto_dp&th=1&psc=1
Or, if you just want the individual cable, you can find that here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
You would need the RMi/RMx series cables for compatibility. The kit and cable listed below will be what you would need. :)
These ones right here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
Full kit if you want that, here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ2BB9JZ?ref_=ast_sto_dp&th=1&psc=1
The 4x8 would just add additional redundancy. Both the 3x8 and 4x8 options would work for you though actually.
You can find the cable you need here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
This would be compatible with your PSU and GPU. :)
Unfortunately we only have the 3x8pin to 16pin one for your PSU (which uses the same as Corsair) on Amazon: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1 - so not the 16pin to 16pin. It's still a direct cable, just uses the 8pin ports of your PSU instead of the 12VHPWR one.
You would want these options here.
Individual 12VHPWR cable: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
For your PSU, these would be the compatible kit/cable links.
Individual 12VHPWR cable: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
Our 90/180 adapters aren't out yet, looking at February on those. Timeline and sign up can be found here: https://store.cablemod.com/cablemod-12vhpwr-right-angle-adapter/
These would be our compatible12VHPWR cables for your PSU: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
Working with something so compact, definitely sign up for our 90/180 adapters here: https://store.cablemod.com/12vhpwr-angled-adapter/
These will be coming in February, full details of that on the landing page link there. The length of the cables are always provided on our products, but if it is too long, you could hit our configurator where we offer custom lengths. That can be found here: https://store.cablemod.com/configurator/
Let me know if you need anything else. :)
No, unfortunately not. If you have a 4x8 option, you MUST install all 4 connections. So you would need to order a new cable in the 3x8 variety. These would be ModMesh, but we have 3x8 options on Amazon with PRIME shipping: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
This one: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1 - PCIe cables are the same for Type 3 and 4. :)
These kits/cables would be compatible for your PSU and GPU. :)
Of course, that can be found here: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1&psc=1
Not sure about the stiffness of Corsair's cables though as I haven't used those myself. ModMesh is our stiffer option, but it's still plenty flexible for builds, my preferred option in fact and the favorite for many which is why we stocked this one first. It provides great aesthetics and vibrant colors for a nice *POP* to any build. :)
The links I'm sharing here will be direct replacement cables for your PSU and GPU. :)
Cable kit with 12VHPWR cable: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ2BB9JZ?ref_=ast_sto_dp&th=1
Individual 12VHPWR cable: https://www.amazon.com/CableMod-ModMesh-Sleeved-12VHPWR-Corsair/dp/B0BJ26HZYK?ref_=ast_sto_dp&th=1