You should be fine mate I am using a power supply with mine RTX 3070 over here and the power supply has just one connector with 6-pin and 8-pin plug maybe I should try to share a image of what I'm talking about maybe it's related to what you are telling us right now
https://i.imgur.com/xoZS5xf.pngIs that it? If YES it works fine
Is the wire with the green arrow a 6 pin? Not quite clear from the picture. But if it is then yes that's what I'm trying to do!
