Newbie question about import and photo backup.

I have a large 1TB Apple photo library (optimised on iCloud), as well as an almost perfect mirror on Google photos using their storage saver option. I want to use immich as either my main or backup photo app depending on how it works. I actually don’t mind Google’s compression, and it takes my library down to 280GB. My plan is to use Google takeout and do an initial library import into immich. The issue with that is if I plan to use immich backup on my iPhone, it will import all my full res Apple photos too.

Therefore, is there a hybrid solution whereby I do an initial import of my Google library, and then Incremental imports of my iPhone library using something like parachute app, and have immich reference this external library as well as the Google local library.

Thanks for the help.