If you could play the full release version on GeForce now, I believe your saves should be compatible with the Mac version when it releases, as the savegame incompatibility was related to Early Access, so shouldn't be a problem with the release version. And I believe that it's been confirmed save files for different platforms are compatible.
But I'm not an official source for that, and don't have a Mac or use GeForce now myself, though, so it is best to be sceptical!
