My point regarding TDP is Nvidia and AMD (and Intel for that matter) calculate TDP differently, plus TDP is Thermal Design Power and not power draw.
Fx. 480 has a TDP of 150W, BUT the power draw is around 164 for the reference model(stock). To make matters even worse the GTX 1070 has a TDP of 150W but a powerdraw around 148W. This is super confusing, and it properly will be too for the Vega card, but we can't say much about powerdraw until the cards are tested. :)