I have a Sapphire Fury and I haven't found the limits yet but did a few simple changes and this is what I get on Claymore Zcash

-72mv 1000mhz core 500mhz Vram 440H/s runs at 55c at 60% fan

1100mhz core 525mhz Vram 480H/s running around 63c a about 70% fan

Hope this helps, getting a power monitor soon so I'll see the difference in power draw soon, I got it the same price used as a RX480 so it is great value.