Yes, that was my point. Pulling everything through one rail is a bad idea. It would work fine with two or three 1070's but I would spread the amperage across multiple rails when possible. I guess I misunderstood your post.
Correct, 2 cards max at 1070 or ti per rail. 1 x 1070ti = 200 to 230 watts at 100% with peaks to 290 watt for less than 50ms. 2 of these per rail max, personally I would do 1 per rail. 16 awg cables = 300 watts per cable in my opinion, or 1 card.