Moving Photos app folder and albums to external drive while preserving organization and metadata

Do you really want the albums as folders in the Finder and not as part of the library?

To save the structure of the folder with the albums and all metadata and adjustments, I would not export to the Finder, but use a partial library, like Servant of Cats suggested, but without moving photos between libraries. Exporting from one library and reimporting in a new one will break the connection between the originals and the edited versions. And Importing directly from one library into another library will only import the media, not the albums.

When I want to save the photos from a folder on an external drive I simply duplicate the library by dragging it to the external drive. Dragging to a different drive will create a copy. Then I open this copy in Photos and delete all photos but the ones in the albums I want to save. smart albums are helpful to select the photos that are outside the date range that we want to save.

If you own PowerPhotos, you can open the Photos Library in PowerPhotos and simply drag a folder with photos from one library into another library. This will work even, if you are using iCloud Photos.

Yes, if you want to retain the metadata of each photo. There is no mechanism to export a folder of albums out of the library. It has to be each album's photos to a corresponding folder on the external drive.

If you have renamed the photos in the Title field then select the Title as the resulting filename upon exportation.

If not there are several ways to export an album and rename the exported files:

Or you can do as I do and use this AppleScript to rename the photos in the library and use the Title for the exported file name:

The Apple Script is Batch Change Title to Text w/Padded Sequential Numbers

and can be found with many more in the user tip Thematic Index to Photos for Mac related User Tips. - Apple Community

I suggest you experiment with export options on a single album to get what work best for you. Then apply that to the rest of the albums you want exported.

NOTE: it's recommended you have a backup plan for your current boot drive, i.e. like Time Machine, and make sure you have a current backup before any major change.

For whatever it's worth, there's this:

Create additional photo libraries in Photos on Mac - Apple Support

Import photos from another library in Photos on Mac - Apple Support

What I don't see in these Support articles is a way of cleaning up the original library by deleting photos that were in the original albums, and only in the original albums. (Photos can be in multiple albums – so your library might have some photos that are in albums you want to move and albums you don't want to move.)

I would like to add that images in Photos have more information with them than picture files in Finder. For instance, an edited picture in Photos can always be returned to its original state and re-editied, but that's not so with pictures in Finder.

About keeping Archive libraries on external drives, as léonie and Servant of Cats suggested, this is a good resource:

How to keep the iCloud Photos library small and archive other photos locally on a Mac - Apple Community

written by léonie. I too, use a smaller Favorites Library which I keep on my Mac connected to iCloud Photos. Then I have other external drive archive libraries for pictures I don't need to see all the time.

You'll have to export each album as jpeg or unmodified original files:

OR