MSI Radeon RX 580 Armor 8G OC 8GB

Hello, I'm thinking of building a rig with this gpu, but I'm not sure about it's performance/watt.
I've read somewhere that you could get approximately 30Mh/s with very low tdp, all this with OC + custom bios.
What do you think about this GPU?
Also, would it work well 6 of these with the MSI Z270 Gaming Plus? I know that it's a little bit expensive but It's hard to find avaliable mobos these days,,,

Thanks a lot.