I was thinking, we can do a two-pronged approach:
1) Main path is 20/21/22 creation, either by uploading something or referencing a URL (we can add a "source" tag, so that it preserves the original webpage link).
2) But:
If someone tags _their own event_ with #pic #vlog or #reels, then we treat the media in that event like a kind 20, 21, 22 event, and pin it to their boards.
If someone responds to _someone else's event_ or to _their own event_ with the same tags, then we pin it to the responder's boards.