AMD has a tendency of pushing clock speeds way beyond their most efficient area to increase price/perf in desktop gaming GPUs(As with Fury[non-Nano], Polaris[80/90], Vega), so I think even if they had an arch that could be quite efficient in the 50-150W TDP range of most laptop(Or console) GPUs I think they'd probably have no issue with launching it in a 225W form for desktop GPUs if they could squeeze out like 10% extra performance from that 50% power increase.