Thank you all for your information.
All higher-end gpus have 2 or 3 connections, so if for example i power 1x3070 which has 2 connections there should be no melted connectors? because 2 connectors would be able to support up to 300W?
If so, then this melted connector problem should only apply to really powerful cards, like 3080ti, 3090
You also have power coming from the PCIe slot, usually max 75 Watts. Average is perhaps 30-50 Watts from the PCIe slot. So if a GPU is pulling 300 Watts then from the PCIe external connectors it uses maybe 250 Watts max. Hence 2 connectors are more than safe.