Hey there,
 
I was wondering... as the 970 has two 6-pin ports on it for power should I use the cable with 8-pin (from PSU) to two 6-pin connectors or should I use two separate 8-pin to 6-pin cables to power the GPU? ... or does either work?
 

This is the first one which I would use just this one cable.
 

and this is the second, which I would have to use two of.
 
The only thing I don't like about the first cable is that the because each of the 6-pins has a detachable 2-pin part (why, I've never seen a GPU with 8-pin for power..) I have to have both folded back to the side and I feel like it causes some stress on the power ports when plugged into the GPU.
 
Thanks in advance for your help.

I thought it might work either way, but I just wanted to make sure that either using one cable'y' type cable so to speak didn't provide a shortage of power, or using two separate cables gave too much juice.

Never Use A "Y" Cable when it come to PCIe Power.
Most PCIe Power Cables come with One 6+2 Pin or Two as what the OP has or One 6+2 Pin and One 6-Pin.
You can use One Cable with Two Connectors or Two Cables and use one Connector from each cable.
The Y cable that comes with a card are for users who DO NOT HAVE 6-Pin PICe Power Connectors.
They are used to connect Two 4-Pin Molex Power Cables to make ONE PCIe 6-Pin Power Cable.
I have Graphics Cards that use Two 8-Pin Power Cables as well as some that use One 8-Pin and One 6-Pin PCIe Power Cables.
 

This computer has 6 Each 6+2 PCIe Power Cables connected to 3 Graphics Cards.
Each card uses 2 Each 6-Pin PCIe Power Cables.

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I thought it might work either way, but I just wanted to make sure that either using one cable'y' type cable so to speak didn't provide a shortage of power, or using two separate cables gave too much juice.

"using two separate cables gave too much juice" Will use no more power then one cable.
"using one cable'y'" I take it that you mean One PCIe Cable with two Connectors on it, if so I would not call this a "Y" Cable.
 
Here are some "Y" Cables.