If there's sidequests, there's still a chance! :p they can still technically go up.
Honestly, Aerith and Red's are the most "story" relevant.
Tifa's is nice. Barret's is nice. Yuffie's is hilarious. The "guy's night" is also super funny.
Aerith's semi confirms a lot of stuff about Cloud/Zack, or what she thinks of Cloud at least, and Red's has lore about the whispers.
Which is maybe why Red has the most sidequests before chapter 12? I think if you weren't trying to game the game for the date you want, you'd likely end up with Red or Barret.
I was trying to game it, so I did all of Aerith's quests and hard stopped for everyone else, so that she was the only person with the light blue icon going back to Gold Saucer.
I feel like I've done almost every side quest up to Chapter 12 and only Aerith is light blue but a few other characters are the dark blue
Maybe I missed some early quests
I got what I wanted anyway, but I didn't really care