Where to put image information?

I guess IPTC/XMP-dc ObjectName/Title would be the place to put that info.

There is overlap in the old IPTC and new XMP-dc tags. You never know which app supports which so it is best to sync them to be the same (GraphicConverter does this by default). Monterey Photos.app supports the following:

[IPTC]          Caption-Abstract                : Caption/Description
[IPTC]          ObjectName                      : ObjectName/Title
[IPTC]          Keywords                        : Keyword1, Keyword2

[XMP-dc]        Description                     : Caption/Description
[XMP-dc]        Title                           : ObjectName/Title
[XMP-dc]        Subject                         : Keyword1, Keyword2

Then there is also this AFAIK legacy tag that for some strange reason iOS devices use and Photos.app prefers over those IPTC/XMP tags:

[IFD0]          ImageDescription                : Caption/Description

GraphicConverter can sync also IFD0:ImageDescription by setting "Edit File Info (IPTC/XMP) [cmd-I ] > Options > set Exif tags in addition (legacy)".

GraphicConverter can delete IFD0:ImageDescription via Exif > Image Description > Remove. Or Exif > Image Description > Copy Caption copies XMP-dc:Description to IFD0:ImageDescription.

Delete via exiftool does the same:

exiftool -m -P -overwrite_original_in_place -if '$IFD0:ImageDescription' -IFD0:ImageDescription= .

Captions from Images are gone - Apple Community

You can put the info in the Caption field of the Info pane and add the Caption field to the Contact sheet print.

You can set as many columns across as you'd like.

Or you can use Pages and place the photos on the page, resize as necessary and add the text below each photo.

Are you using iCloud Photos, Keith, and also iOS devices?

I am entering all metadata twice or three times in Photos, because of the inconsistencies Photos between Photos iOS and Photos for Mac, as titles, captions, keywords.

• The titles can be displayed on the Mac below the thumbnails, also exported and saved with the edited versions and printed in a spreadsheet. On the iPad and iPhone the titles are only shown as a search result. I need the titles on the Mac below the thumbnails.
• The captions can be displayed in the Info on the Mac and the iPhone and iPad, so I need the captions on the iPhone and iPad. My Mac is including the captions when sharing the photos in shared albums, but not when exporting the photos with File > Export.
• The keywords are only visible in the Info on the Mac and as search results, but not in the info on the iPhone and iPad. But they are reliably exported when exporting edited versions. So I am using the keywords to transfer photos between libraries or to share them with other people.

PowerPhotos will include the titles, captions, keywords when moving photos between libraries, but Photos for Mac is omitting the keywords.

I recommend to wait for the final release of macOS 13 Ventura, to see how Photos duplicate detection and removal will handle the metadata tags when merging duplicates.

For the time being I am very cautious and are adding the information to all suitable metadata fields, to be sure to preserve the information.

"My Mac is including the captions when sharing the photos in shared albums, but not when exporting the photos with File > Export."

For me, when I File>Export pictures, they include the caption, keywords, titles, locations, and people. It also includes other things that I may have included with the photo before I imported to Photos. I use GraphicConverter to look at that stuff.

Oddly, if I just drag the photo to the desktop and examine it, the caption and location are there, but keywords, title, and people are gone.