There's one thing I haven't understood yet...
These regedit changes are for Vega64 only, or they also improve the Vega56 above the 1850H/s from wattman alone?
I'm unsure if I should stop the miner or not to try that out

Worst case scenario I end with my wattman problems when one gpu decides to reset to default values, but I wonder if with 64 bios and the same vega 64 values the V56 can also reach stable >1900s
I am interested to see if any of your vega 56s will make your system not boot(after registry edit), like it does to some of use unlucky ones with vega 64s.