buy some sample paints, paint them on the walls (or cardboard), and see what undertones come out. we can't truly help you with it, as it entirely depends on the kind of light you get, what direction the windows are facing, etc. even the number of green trees outside your windows impacts interior color, and the color of your flooring / furniture, etc.

IMO you need to test paint in the space with the lighting all on . That means no painting until you have at least got access to the home to paint large poster boards and move them around at all times of the day and in all the spaces . Make sure all the lighting that is there is LED 4000K to make this simple . I find Alabaster a bit creamy usually do you want a warm white ? Your flooring , your furniture will all have an effct on wall color so keep that in mind. There is no reason to have to paint before possession IMO so maybe explain that . I actually find Greek Villa has more yellow or green undertones in some cases .BTW you neer use cardboard to test paint color go and get large white poster boards and 2 coats of paint.

Confused. All alabaster? Or alabaster with white trim and ceilings?

We’re going to paint the whole house (walls, trim, ceilings) the same color for now amd we’d like it to be a neutral/white without being too stark. I’ve been stuck on alabaster (SW is the only option and I’d like to avoid color matching) with highly reflective white or extra white for trim and ceilings.

Alabaster is a warm white, but as the other posters are saying, it's hard for us to know if that will work for you without knowing anything about the floors or your furnishings. Isn't there any way you can get access to the home for a half hour before closing so you can take over some sample boards? It is customary in our area to give buyers one short visit after inspection and before closing to be able to come over with a contractor (if they're contemplating an immediate remodel), or samples as you need to do. Ask your real estate agent if you haven't already if that would be possible.

I understand wanting to have it done before you move in because it would be nice to not have the workmen underfoot, but it is very expensive to pay to have a whole house painted, especially if you end up hating it and have it all redone. If the current owners have some really horrible colors in some rooms maybe just do those couple rooms? If it's all terrible, maybe it's not a bad idea to get a clean slate. Have you used a neutral in your current home that works with your furnishings that you could use again?