I think I might have just uncovered the reason the Fury Nano performs so poorly, and it has to do with Wattman. My Wattman settings are set to automatic fan speed and a temperature of 75*C (default is 85*C but it heats up to that just as fast as well). This in theory sets the Wattman fan curve to peak out at 75*C, but instead it causes massive throttling to stay below that target temperature. The Fury Nano, being an ITX sized card, doesn't have the large heatsink of every other card, which causes abnormal performance as the heat ratchets up faster than the fan speed can adjust, since it slowly ramps up. I'm short on time right now, but when I return I'll do a run with the manually set fan speed to max and highest temperature and compare results to the one as before.
But in the meantime post your results on here using the 1080P Extreme preset, it only uses 3800MB VRAM so it won't be affected by 4GB cards, and see if you experience the same kind of result.