I’m on track to finish base coat and shading my rebels this weekend. I’d like to actually get a game in with them, but want to highlight later. Would it be okay to spray a matte varnish now and return later for highlights? Or if I varnish now am I stuck with what I’ve got?

You will be fine but if it was me I wouldn’t even bother. You would have to be playing with them pretty roughly for paint to get chippd or stripped away in just a couple of games. The worst that would happen is you would have to do a quick touch up so I say just go have a game or three and not worry about it.

Agree with EyeSeven, especially on plastic minis paint chipping isnt much of a problem. Youd have to be pretty rought with them for it to become an issue!