If you can take your time with overclocking and downclocking you will eventually get the best settings for RX580, here is what I'm using presently that's giving me 30mh per second with 90 watts, my RX 580 Is also micron memory
Core clock 1070
Memory clock 2136
Fan speed 70
Core voltage -162
The trick is reducing the core voltage to limit energy consumption, use msi afterburner and unlock the core voltage in settings
Is this the maximum electricity draw for RX580? I've read online about some getting 80watts at 30mhs, maybe it's because your graphic card is Micron based memory? With 90 watts power draw if prefer to adjust the clock more, 32mhs looks good