1. Yes it depends
2. It's a good start
3. I get's 31,140 Mhz per card on my RX470 4GB rig and 34 Mhz per card on my RX580 8 GB rig just under 900mV (I cant' go under 900mV and I don't know why...)
4. The power consumption I was talking about it's the "GPU Power draw only" item from GPU-Z
2. good start is 836 and make it stable
4. dont use GPUZ for volts monitoring, use HWinfo64 instead properly configured for sensors only and "not invasive" scan of busses, nor AFB (even if I have Afterburner installed I disable it from autostart normally- its VERY bad shit, even though sometimes can solve issues)