Now, the voltage.

i have 3 RX 570's nitro+ 8gb

1º 1150/2250 831-837mv core/ 1000mv mem 31.4mh/s
2º 1150/2190 831-837mv core/ 1000mv mem 30,8mh/s
3º 1150/2125 831-837mv core/ 1000mv mem 30,3mh/s

They were stable for months at this settings. I tested for two days all of my cards before going into the mining rig. i programmed the bios in all of them and i tweaked as much as possible the voltages except for memory. ETH is a pretty intensive algo with the memory, and i prefered to forget about having problems with undervolting. I suppose your undervolt saves you some money.

my 2x6 mining rig are off. and they will continue to be off for a large period of time. I will only turn them on if i can get 100$ profit per month or more after electricity bill, which i think will not happen this year.  At current prices , and the very expensive cost per kW i would be losing around 15 $ for month with bills of around 350€ or a bit more in summer due to fans having to work hard in my room to deal with heat, specially where i live.

So....yeah...mining is not worth for me.