Metadata lost when downloading photos from iCloud

I have read several posts on this topic, and I simply cannot understand why this isn't working.

My usecase is this:

-We have a Photos library that is huge, with all family photos from 20 years back on our iMac. This album is not on iCloud for cost reasons.

-My wife takes a lot of photos with her iPhone. This is a company iPhone, with a company Apple ID.

-Recently she swithched jobs, and now we want to "empty" the iCloud account for that Apple ID. Mainly this is about getting all photos from that account to our family photos library on the iMac.

-I have downloaded all photos that we want to save, but when I import them into Photos, they are sorted as if they were all taken on the date of the import (or the date of the download... it was the same day). In real life, this is not the case, and on iCloud they are still sorted in calendar order.

-The metadata seems to be lost when downloading the photos.

-I have read in similar posts that I am not alone with this problem. One solution is apparently to create a new Photos library on the iMac, and simply synch that one to my wife's old company Apple ID. However, when I select to synch with iCloud in the Photos Preferences, there is nowhere for me to specify which Apple ID I want to synch with. It is not the one that is the "general" one that I use for the iMac. This is a "one-time" synch with another Apple ID.

Does anyone know how to specify from which Apple ID to synch photos, or does anyone have any other solution to the main problem (importing photos from iCloud with preserved metadata)?

Many thanks in advance. :)