Hey, THANKS, jerryy!! I found all kinds of online references about the Photos app that say you just have to play with the settings to see what you can get, but nowhere a hint of this. Here's the same image, exported from Photos as a full size full quality jpg, and then re-exported from Preview with the slider set to just under 1 MB:
Open your “final” image in the Preview app and re-export it:
https://support.apple.com/guide/preview/welcome/mac
scroll down to the “Convert … “ section.