Yes you can. Even at full power you would have enough to run both RX 580. But also know you can alter power settings to make them run at less power.
The quality of the power supply is very important. You don't want to cheap out on the power supply.
https://linustechtips.com/main/topic/631048-psu-tier-list-updated/Stick with tier 1 if you can. Tier 2 if you can't. Tier 3 only if you have to and for 1-2 GPU systems only.