So got a Vega 56 to play around finally.
Mining cryptonight @1926 H/s with xmr-stak at 1408 core and 925 HBM2 (900mV).  Even though the overdriveNTool profile is set to run at 1408/915mV HWinfo64 says the CVDDC is at 1.25V.  MVDDC changes get reflected but not the core.  Any pointers?
I am already using soft pp table btw.

Core   P6 is 1212, 910 mV and P7 is 1408, 915 mV
HBM2 P3 is 925, 900mV