use the VGA cable to power riser & GPU.
Is it ok if I use one VGA cable to power a gpu and the riser for another gpu all on the same cable?
each riser & gpu combination should be connected to same PSU. you can use one VGA cable for the GPU and the riser connected to that GPU. or you could use one VGA cable to power multiple risers, but it would be easier just to use one VGA cable per gpu/riser combination. you probably need the splitters linked to on ebay.
if you're keeping your GPUs under 120 watts (like around 90-120 watts) you could put 2 GPUs on each VGA cable. I think those VGA cables are rated for 300 watts, running 225 watts on one VGA cable would be no problem.
I have a rig right now where I have 2 GPUs per cable and I keep each card under 110 watts. no issues
the issue is my psut doesnt have any VGA cables with two 8 pin connectors on them so I cant string two gpus on one vga cable (since my 1660tis all use 8 pin connections).
tbh, while doing my homework for my rig I think I read that its better to not use any extensions, splitters, or converters for the PSU cabling since the more connections the higher chance for an issue, aka fire, etc. So thats why I would rather not add a extension for the 6 pin connector on my cables just so that I can keep both the riser and the gpu on that riser on the same VGA cable.
If its advisebale I could power a gpu with a 8pin and then use the 6 pin on that same cable to power the riser of the gpu hanging above that one. And then I could use a 8 pin cable to power the gpu that is handing above the first gpu. They would all be on the same psu.