"new settings" ?? Here's a guide I put together (RX580 is just an OC'd RX480)
You don't need Afterburner when AMD's WattMan utility is already installed and running within the driver suite.
My best advice is to test and record the lowest stable voltage at multiple clock speeds and graph the results. That will give you a very simple curve to extrapolate from. Once you get above 950mV, the slope of the curve will change.
With GPU overclocking, you're working against two limitations, the max frequency the chip is capable of, and the power(voltage) limit (which also corresponds to temp). Because of this, you won't get the same amount of OC by leaving voltage on "auto" as you will if you set voltage to "manual" and test for the lowest stable voltage. By doing that, you're doing your best to stay away from the power/voltage/temp ceiling and let the chip frequency be the limiter.