Riser +gpu need 3 cables. Cards takes 200-220w, riser 0-40w? In total max 260w, but two 6 pin cables can do 300w. Could I do with just 2 cables?
Cable 1 - 6 to 8 pin - breakout board to gpu ?
Cable 2 - 6 to two 6 pin Y cable - from breakout board to gpu & riser.
if they are quality cables and you set tdp to 190 watts or 76% yes it should be good