Galaxy 1.x has had cloud saves for ages, so unless GOG are doing the Valve thing of breaking/removing existing features in the process of adding new ones, I’d expect cloud saves to work the same way in 2.0, assuming the game in question supports it. As for other games, I imagine it just defers to whatever, if any, cloud save support is present on whatever platform the game it’s launching natively supports (again, assuming it supports cloud saves their too). My understanding is that 2.0 doesn’t necessarily remove the need to have the Steam, Epic, uPlay, etc launchers installed and running, it just provides a unified interface for managing and launching games across all of them.