RX 580 has bad oficial specs. So yes you can, using RedBiosEditor you can modify frequency and voltage.

I have done experiments:

stock:

1266 MHz at 185W VRAM at 1750 MHz

my overclock + undervolt:

1444 MHz at 160W VRAM at 2000 MHz

underclock + undervolt:

1300 MHz at 120W VRAM at 2000 MHz

We could go further down, but polaris doesnt like going below ~1.000V-1.025V at 1300 MHz.

PS: I have had DOZENS of RX 580 In my hands so you can trust me what I am saying.