Currently Online 
Microsoft likely hasn't paid for exclusivity, of course they paid for Game Pass and that might be why they're prioritising Xbox, also Xbox's early access is less strict than PlayStation's IIRC but I'd expect them to strike while the iron is hot and try to get it on PlayStation ASAP. As for the performance, like I said before, it runs a lot better on Steam than Xbox, the Xbox version is a few updates behind (1.0 vs 1.2) because of the Xbox certification process, it is a lot slower than Steam's, in fact, does Steam even have one?
I think developers can just push updates to Steam whenever but they have to wait sometimes weeks for Xbox which of course slows things down, the Windows Store uses the same Xbox certification process as well. This becomes a more noticeable problem for early access titles which sometimes can have dozens of updates in quick succession due to the nature of them being early access.
