If you are asking if you can use a power supply that has two 6 pin or two 6+2 pin adapters on a single cable, can you use just one of them? Then yes. Otherwise, you haven't asked a coherent question ...
If you are asking if you can use a power supply that has two 6 pin or two 6+2 pin adapters on a single cable, can you use just one of them? Then yes. Otherwise, you haven't asked a coherent question ...