I don’t do anything special for photos appearing in multiple albums. My use-cases don’t align to that.
My whole photo-taking process tends to be:
* take a bunch of pictures
* find the best ones
* further refine the best ones until it’s a reasonable number
* photoshop those to how I want them
* share the narrow list
And most of my photos come from events, so they’re in folders based on events.
If your goal is virtual galleries and avoiding duplication, this is sufficiently different I don’t think I can give suggestions there, I’m sorry