OCC published a look at RX Vega 64 Efficiency
A quote from the article:
This has definitely been an interesting project for me, and one I am very glad I decided to do. Of course the surprising results of Killing Floor 2 made it worthwhile, but so too do the results for both Wolfenstein 2: The New Colossus and Middle-earth: Shadow of War, just in different places. Across all three games we saw a noticeable drop in power use when undervolting and not limiting the frame rate, or using a high limit. This reduction in power use is important as it improves the efficiency of the RX Vega 64 and it allows increased clock speeds with the reduction of thermal throttling.A Look at RX Vega 64 Efficiency