I currently use SRB to mine XMR.

The timings of both my RX 570 are optimized with Polaris Bios Editor 1.6.7 which gives more performance than SRB Polaris.

RX 570 4G Samsung
GPU 1280 MHz 990 mV
Memory 2110 990 mV
989 h/s

RX 570 8G Micron
GPU 1280 Hz 980 mV
Memory 2220 Mhz 980 mV
977 h/s

Their config for SRB Miner is pretty simple:
  { "id": 0, "intensity": 0, "threads": 2},
  { "id": 1, "intensity": 0, "threads": 2},