This is my setting:

RX580 Sapphire Nitro + (Samsung) 4gb

{
"cryptonight_type" : "normalv8",
"intensity" : 59,
"worksize" : 8,
"double_threads" : true
}

Wrosksize can 8 or 16 doesn't change much.

Best card 989 H/s, worst card 973 H/s

OC:

Core 1260
Voltage 900mV

Mem 2120
Voltage 900mV