I played with this tool during the weekend on Vega.
But to be honest I did not see any hashrate increase under CN algos.
I'm not an expert on timings, but I should see at least 1-2% increase when changing CL 20->19

That was the first time I put a Linux AMD system together and I am struggling with the different kernel and driver versions not working together.
The biggest problem is the GPU freq is affected by the voltage.
If I set in PPT P7 1600 950 then the GPU runs only at around 1400@950mV. If I increase the voltage the clock goes up, but quickly reaches TDP.
Also if I try to trick it and set P7 1700@950 then if load changes freq spikes up and card freezes obviously.
Tried with 3 different kernels and one is worse than the other.
Maybe I should try other than the 18.50 amdgpupro?