Our problem: Sharing of albums is very limited. The user who created and shared the album seems to have full access to all photos in full resolution. So far so good. However, invited users can only access the photos in reduced resolution. Also, invited users can't search or filter the album, nor can they copy the photos to their own albums, or add them to their own catalog.
So, to achieve what we want, we would have to go back to Dropbox/Drive/etc. and collect the raws / high-res JPGs there. That has to work better, doesn't it?
The situation is different depending on whether the user has a subscription or not. So for the two of you with existing subscriptions, and assuming the album has been setup as a full "contribute and edit" album:
1. Only the owner of the album will have the ability to copy photos contributed by the non-owner into their own albums, i.e. basically when user B contributes an image to an album setup by user A, user A will be able to use that image as if it was their own.
2. However, both of you should have access to the full raw image, not a lower resolution version. Both of you can export any of the images in the album, including the "Original" option, i.e. a copy of the raw file with settings.
3. Both of you should also be able to filter on that album as per any "normal" album.
4. The contributor will be able to see all metadata added to all images in the album, but only the album owner can edit that metadata.
The non-subscribers will be more limited in what they can do. If they have an Adobe account, they should be able to access the LrWeb portal to view the shared album. They can contribute new images to that album, and they can even edit images in that album (assuming they have "Edit" authority). I think they would be editing the raw file, but they are currently restricted to a "Fit" view on the screen, there is not a 1:1 view option (that applies to LrWeb generally, including for subscribed users). They can only download a jpeg version (though that should still be full resolution). They will have access to all metadata (keywords, etc.) associated with the images in the shared album, but cannot edit it, and of course LrWeb is more limited than LrDesktop in search/filtering options.
Finally, some another related question that I can't find an answer to: What happens to his photos when an invited user deletes his account / cancels his subscription? Do they disappear from the album or do they remain?
When a user contributes an image, they have (I think) 48 hours for a change of mind retraction of that image. After that, only the album owner is able to delete it. When it's contributed, it is copied from the contributor's cloud storage to the album owner's cloud storge (and it counts against that allowance), so once the 48 hours is up I doubt that anything could happen to the contributed images even if the original contributoe cancels their subscription.