Cryptonight on Vega is very high profitability right now, if you can get your Vega doing the frequently quoted 1800-2000 hashrate ballpark (this seems to require use of Windows 10 or PERHAPS LINUX, though I wonder how you get the cards to undervolt enough in LINUX to support higher core clocks without overheating or exceeding TDP).
Forget trying it on Windows 7, even though AMD *CLAIMS* the blockchain driver works on 7 it does not work AT ALL in every attempt I've made to get it working - either constant crashyness on known good hardware, or doesn't recognize the GPUs at all.
The $399 price point for Vega 56 seems to have been a VERY short lived abberation - 2 or 3 days at most.
I have 2 x 64s (Sapphires) and 2 x 56s (GA) coming next week -- so whats my chances of getting these to work on WIN10 ?
Good - and at this point that is your ONLY choice for getting high performance out of them, as AMD is being VERY VERY SLOW about getting Vega support working in AMD-GPU Pro for LINUX.
After much pain and tribulation, I DID finally my 56 to run at high speed on XMR - using Cast as I'm pointing the miner at Nicehash for now and XMR-Stak STILL does not support Nicehash.
It's a major pain having to "disable" and "enable" the card after EVERY BOOT to get it to do high speeds though, but nothing else I tried out to get it to work right gets the job done.
Usage of Afterburner vs usage of JunkWattman doesn't seem to matter - neither support undervolt on the blockchain driver, and otherwise they're more or less equal about getting stuff configured (except that Afterburner STILL blows Wattman away on fan control, NO CONTEST, and is just overall easier to use and work with by a TON).
Sapphire Vega RX 56, not BIOS flashed (though Cast identifies it as having 64 compute units ANYWAY), runs about 1940 hash/s at -10 TDP 940 memclock and core downclocked in Afterburner to 1400 (or -10% core on Junkman).
Didn't play much with the settings, as it seems like adjusting them CAUSES the hashrate to back down to the under 1400 range every time I tried until the "uninstall/reinstall" trick is done AGAIN.
I also noticed that adjusting the settings caused the memory clock to reset to 800 Mhz and NOT BE FURTHER ADJUSTABLE a lot of the time - which contributes to the low hashrate issue.
Not sure how long I'm going to put up with this very unstable BUGGY AS HECK setup, as I have another use I'd like to put the card back to.
I can verify that Cast doesn't seem to CARE about that "HBCC" setting in Wattman - if I had this whole mess to do over again, I'd install JUST the driver and nothing else in the hopes of eliminating some of the buggyness.
Whats the other use you'll put it back to and @Citronick have you gotten your cards yet?
QuintLeo has the setup gotten any better? If you've gotten it stable it has to be pretty lucrative
That's awesome I helped get you into mining / I owe it to this forum for helping me to get into mining so I'm glad I can make a semi decent tutorial xD 
