How Do I Move Photos & Retain Metadata?

My goal is to have the well-organized photographs available from any device that can access my iCloud storage, most often that would be my iMac, iPhone and iPad.

if you copy and paste, or drag and drop from your Photos Library on the Mac, you not only lose the metadata, you will also reduce the quality of the photos.

Use the Photos.app on the Mac to organize your photos. You can create albums in Photos, and related albums can be grouped by folders. The albums and folders will sync with iCloud Photo Library to your iPhone. The folders can be nested. You could create a folder "Kayaking" with subfolders for each year or location, and then an album with the photos from each kayaking event.

If you need folders on the disk as well, to be used from devices that cannot access iCloud Photo Library, use "File > Export > Export .... photos" and use the checkmark to include all metadata.

Yeah, this does not work. There is no box to check "include metadata", only boxes to include "Title, keywords, description" and "location information" and with these boxes checked, still lose metadata. Photo description says photo was created at the time the export was done. Terrible feature. Makes backing up photos and organizing very difficult.

Use iCloud Photo Library on all devices (use optimized photos on devices with limited storage) and do not use the finder at all - use albums and folders in Photos adn they will be available on all devices and all changes (additions, deletions or edits) made on any device will be made on all devices

https://www.apple.com/icloud/photos/

LN

1 - no - Photos is a database program and it works on a library basis - each photo is in the library once (and only once) and it is viewed in different ways - Photos, All Photos, Last Import, etc are not places but simply logical views of photos in the library - you can not remove the photo from the library and still view it from the albums

2 - import them into Photos adn organize into albums (using folders too if you need a hierarchical organization

3 - same as 2

LN

I can organize photographs that are in my System Photo Library by creating a folder there to store albums and then dragging photographs into the albums, but the photographs also stay in the System Photo Library. So it seems that I'm now storing them twice and wasting iCloud capacity.

Photos is storing each photo only once, even if you add the photo to many albums. the albums are just grouping the photos differently, but they do not copy the photos - they are referencing the same photo in the library.

Photo description says photo was created at the time the export was done. Terrible feature. Makes backing up photos and organizing very difficult.

The date in the Info for an image file in the Finder is always showing, when the file has been created.

But that does not meant, that the original EXIF Metadata will be lost.

Photos is including the original EXIF and IPTC tags, when exporting a photo with File > Export > Export ...photos. Any decent image editing program will be able to read the original capture date from the embedded tags. Just open any photo you export this way in Preview and look at the embedded metadata (use the command "Tools > Show Inspector" and check the embedded tags. You should be seeing the original capture date, the lens, the camera make, all titles, captions, keywords you added.

only boxes to include "Title, keywords, description"

These boxes are there, because you can omit these metadata, of you do not want to include them. But you cannot omit the capture time or any metadata set by the camera, like shutter speed or camera model.