On my Vega 56:
1550 at ~100 watts (power limit -50)
1800 at ~150 watts (power limit -25)
1950 at ~200 watts (power limit 0)
2050 at ~240 watts (power limit +20)
More power does not give better results because further increasing the memory clock the card gets unstable.
Have a look at:
https://bitcointalk.org/index.php?topic=2256917Vega56 can do 1950h/s @ 130watt.
And no need of closed source 2% fee miner. Open source xmr-stak-amd is just fine ... except 1 thing - it doesn't work with nicehash.