On a PC your saves will be stored in the same folder regardless of whether you're playing through Steam or with PC Game Pass, so you can theoretically easily switch over from one to the other. However, I would recommend choosing one platform and sticking to it (rather than switching back and forth continuously) in order to avoid conflicts with Cloud saves.
As for getting your saves over to Xbox, this should also work as the two Game Passes share the same Cloud service. You will need to play it with PC Game Pass first though, to get the saves from your computer to the Xbox Cloud, before you can access them from your console (you can't go directly from Steam to Xbox). Once again though, you should still choose either Game Pass or Steam, so that the two Cloud services don't try to conflict with each other.
The good thing about crossplay though is that it doesn't matter which you choose - you'll still be able to play with your friends regardless of whether you're all on console, or they're on console and you're on PC.