Emailing images from Photos with titles visible

And here's another possibility-- use Print>Contact sheet.

Unlike the other options, the pictures won't be full sized. But you can make them bigger or smaller than I've shown. If that's OK, you can choose titles, captions, dates, among many options under the pictures. This would print a paper sheet but, after hitting "Print" you can choose instead to save it as a pdf that you can then put in an email.

If those fields are included in the image metadata, and if the workflow and if the mail app does not strip them, then the recipient should be able to see them if the app s/he is using can display it. The foolproof method is to irreversibly "burn" the text to the image's pixel data.

Or, exporting the image file from Photos with the title as the filename.