Power Consumption & Efficiency AMD RX 5xx BIOS Clocks & Voltages

[MrN1ce9uy]

I modify my AMD RX 570 & 580 to set core and memory clocks and voltage in bios because that seems to work best.

I've been running

RX 580 Nitro+ Hynix & Micron
Core 1250 950mV
Mem 2200 1000mV

RX 570 Nitro+ Elpida
Core 1250 950mV
Mem 2100 1000mV

RX 570 Gaming X Twin Frozr Hynix
Core 1250 950mV
Mem 2000 900mV

With those settings I get these power usage numbers

(*Update: I'm asking myself why I haven't lowered the voltage on the other cards like I have the MSI. My answer is I was afraid it would be too little voltage for the higher mem clocks and I don't want to waste any time with the system being down.)

(in HWInfo)
2x RX 580 8GB Nitro+ - 115W (each) 31-32MH/s ETH
1x RX 570 4GB Nitro+ - 115W 30MH/s
2x RX 570 4GB GAMING X - 85W 28MH/s (Mem errors too abundant at 30MH/s)
2x 1070 Ti Mini 70% PWR Limit - 125W
SeaSonic PRIME Gold 1200W w/ Kill-A-Watt Meter reads 1175W-1245W (at the wall) depending to GPU temps, fan speeds, and power limits on GTX's.

The SeaSonic PRIME Gold 1200W has somewhere between 90.6% and 87.7% efficiency at this power load.
https://www.pcper.com/reviews/Cases-and-Cooling/Seasonic-PRIME-1200W-Gold-Power-Supply-Review/Efficiency-Differential-Temp

Do you think that's a safe load for long-term? I'm figuring it's somewhere around 80% load, but I'd like to lower it if possible.

My question is what clock speeds and voltage do most people run their AMD RX 5xx series cards for better power efficiency? I feel voltage could be lower, but what about clocks? Will I have to sacrifice some hashrate?

Thanks