Just do not use sata to molex power adapter, its weak and they are low quality not suitable for RX480, connect molex directly to USB riser
Also do use 2 molex max per rail, to not overload your PSU cable rail
On the market there are some better quality sata to molex adapters but duno if they are good for ~50w which rx 480 can pull sometimes
With the customer AMD RX 480, you can use those SATA to molex power connectors as the requirement from the PCIE slot is lower.