No one answered you, so I'm going to try and help.

1. You can paint the island after you move in, if your construction team won't do it. If it were me, I'd push, push push. But the paint needs to be that catalyzed hardened top notch cabinet paint, so I'd research like crazy before I had anyone paint cabinets. (I think it's called catalyzed conversion varnish, but I am not an expert).

2. You don't need to have cabinet colors coordinate; imho; however, I'd have a bit of a vision for each room.

Sounds like you need a little help. Just having someone smart to help you pick finishes could be a HUGE help to you. It's a lot of decisions.

In the meantime, in your shoes, I would devour all the how-tos and videos of Maria Killam, so you at least end up choosing your hard finishes smartly. That's what I would do. You can follow her on Instagram and start with her "10 things People do to mess up their renovation" (not the exact title, and you don't need to follow her advice exactly, but she sure makes a lot of sense for those of us who can't remodel to fix our mistakes...)

3. No, no need to use the same hardware on all cabinets througout the house. Sounds a little boring to me.

^agree with Mrs S on no need to match cabinets or hardware in each room. I have turquoise kitchen cabs with brushed bronze and white oak vanities with black hardware in both baths ( just cause i liked the wood.. wouldn’t have minded a colored vanity in hall bath either!).
Have never painted cabinets personally so i can’t speak to that one. Maybe talk it over with contractor and see if they can help.
Making all these decisions is overwhelming, I know. It’s a lot all at once. I’m sure it will be gorgeous when it’s done 😊

Thank you both for your help! I will definitely check out Maria Killam!! It’s nice to know everything doesn’t have to blend perfectly from room to room…sounds a little boring 😝. Thank you so much for the cabinet painting advise as well!