Big question for me is - how will it behave when you also use icloud photos as well? And what if it's an encrypted disk?

I'm asking because of the following:

Let's say your laptop is 1TB, but everything except photos and for example dropbox is under 512gb.

If you then need to restore, your new laptop has to be able to contain the full restore (1TB, or whatever is used). This also means you can't just run to the store an get a standard model (instead of built-to-order) and restore, unless you buy something that has enough storage.

Having multiple apfs volumes helps here, and I'd love to have all cloud storage off of my main one.