Worth considering the other A7 lines too, just because you mention night photography.
For example, I know the main differences between the A7r iii and the A7 iii are the obvious one, the A7r has double the pixel resolution, but less obviously, it also has a reduced maximum ISO compared to the A7. Given that’s 30,000 ISO vs 51,200 ISO (and up to 204,800 expanded ISO) at the levels we’re talking about might not matter for what you’re trying to shoot, but it’s worth considering.