No use 2x connector from the breakout board if you have 2x connector on the GPU it's better this way for power load-balancing, especially if you are going to run them @ high TDP.
Im planning on running 2 cables to each card. I didn't understand your response. I guess Im asking if it's an issue to power a dual 8pin 1080TI card with two direct cables from 2 ports on the breakout board?