2012 Mac Pro GPU power supply question regarding 6-pin to 8-pin cable

I have a 2012 Mac Pro 5,1 that I intend to upgrade the GPU to a Sapphire PULSE Radeon RX 570 8Gb GDDR5. The card that is currently installed is the stock ATI Radeon 5870 1GB GDDR5.

I know that the PCI slot supplies 75W and that each of the 6-pin connectors that are hooked up to the 5870 are suppose to carry 75W each. The RX 570 has one 8-pin connector and looks to be rated at 150W.

I don't want to use a single mini 6-pin to 8-pin cable, because even though 150W is the max level for the RX 570 in theory, I'd rather have some wiggle room. I see that they make a two mini 6-pin to single 8-pin cable and am wondering if that would be ok to use. I would assume that it would put less load on each of the mini 6-pin connectors on the logic board.