Just run 1100 MHz on core and 2000 Mhz on memory and you'll fine. Undervolt some like 850 mV maybe.
Is 850mV is the safest undervoltage for rx580 gpus ? Cos some people are using 75 watts mining with their rx580 and I can't get the same watt power draw from my gpu, right now it's mining at 90watts with 850mV using wattman, is there something I'm missing here?