First question: On a 30amp pdu with a 30amp breaker you need to keep everything within that 20-24 amps or 80%. Anything more youll have a high chance of overloading the breaker and pdu
Second question: I am running 23 rx470 cards with 1500 strap mod on a 1050/1800 (core/memory) the cards run around 23-26 mhs mining ether at ethermine.org
https://ethermine.org/miners/31C1C0Fec59CEB9cBe6ec474C31C1DC5B66555B6 with that i bring in around .05 ether per day. my monthly power bill for the cards runs in the 220-300$ range mostly depends on outside temps in florida
you can put 24-26 cards on a 30 amp breaker safely
now heat ill be an issue so make sure you have somewhere for the heat to go
its winter right now so its nice but summer is coming...
Though, I am not very familiar with the RX 470 but I know they run 30W less than the 570's in terms of power consumption. I checked your ethermine.org stats, I'm so impressed by the what I see with the results you get with 1050/1800 mod. Your average and current effective are way higher than your reported hashrate, which is affected by the amount of shares you've submitted.
With my two rigs, 390mh/s it's been opposite of that, shares definitely lower than yours and average and current effective are never even close to what I'm reporting
https://ethermine.org/miners/f8339952A224A228F2f8C58A5666a8Ff1EDdeBFb Was thinking of trying Nanopool sooner for a week as well to see if there's a difference, not after I ping both US servers at ethermine again. Connected to the US2, which is for the west, I'm in Texas and I don't know if it should be the US1.
Ordered the 10-30P to 6-30R adapter that I'll be using to connect the PDU to the dryer outlet. For heat control, I plan on running a box fan on window to take the hot air out, as my rig rack is just in front of the window, going to be moving that forward a little to create ample space behind cos I almost had a bad ordeal with the rain last weekend, never happened before but good I decided to go check the rigs.
I use the Rosewill L4500 4u case for my rigs with a little modification with a 1200W EVGA PSU and the Delta 3500rpm 153cfm fans up front, some cards in the first rig go up to about 77 degree Fahrenheit and the second never surpasses 74, so I definitely need to work on moving air more.