I could downvolt eth only to use ~80w stock clocks, GPU-Z (not at wall, but same card so it's relevant). ZEC uses similar. If you downclock to say 1000MHz instead of 1260, you get same speed on Eth (zec suffers), but you can lower voltage another 100mv or more, chopping off perhaps another 20w (haven't tested yet).
Sure you can downvolt to that extreme but your hash per watt suffers past certain points.
Anyways, good luck doing that 2 times a day per card if you're using the RX series if you're wanting to mine whatever is the most profitable.
Sapphire 470 8GB (1750 strap)
Zec 1260/2000 -i 2 1020mv, 82w GPU-Z Avg, 177H/s
Eth 1075/2000 820mv, 58w GPU-Z Avg 27.5MH/s
You can control clocks and voltages with Claymore's miner easy. Recently Zec and Eth similar profit on Polaris, and Zec is a lot better on 7000/200/300/Fury, so switching on 470 makes no sense.
@xeridea is it easier to control wattage through calymore than through wattmon?
Ive found with wattmon if i go below .96 volt or sometimes even 1.0 core voltage on any card with stock core i crash
You can set voltages and clocks on startup (see thread OP for details). I don't do it because I don't change clocks, or switch coins often, but many others do.
How low you can go depends on the card. For finding lowest voltage, it is better to go to wattman, and do a voltage drop based on stock. Stock voltage can vary from 1050-1156mv, so results vary a lot. I have found generally 960-1030 is lowest stable at stock clocks.
After you find lowest voltage for each card via wattman, you can set the voltages on miner startup if you switch coins, for winter/summer, etc. Just make sure to get card indexes in right order (-di option can help), or volt all according to the worst card).