Both the reference 1660 Super and the RX 5600 XT use a single 8-pin PCIe power connector that can supply 150W plus another 75W via the slot, and when coupled with your Ryzen 5600G means you have a potential power draw of up to 300W. Any decent 500W power supply should be sufficient.
As @franka states however, some card manufacturers may offer overclocked versions of their cards and some may even have dual 8-pin power connectors which could draw more. In that case you want to follow the recommendation of that particular manufacturer for that specific card.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT