63.5 mh/s is rock solid with TRM 0.8.1 under Windows using max possible mem oc and fast timings preset in Radeon Settings.
97 watt by sensor now.
I was able to achieve 89 watt by lowering soc voltage and gpu voltage further but it leads to sudden BSODs ((

See my current stable config in detailed screenshot: (it is XFX merc 319 RX 6800)
https://i.imgur.com/Sr1gvb0.png