for RS:MS, fortunately most quests that require a specific person in your party are early in the game. if you've done the one you take Raphael and Theodore on, the one you need Guella Ha for, picked up Hawke's map one way or the other, and recruited Barbara at least once, you're pretty much good to go. LP-killing Claudia's beasts (who are temps anyway, and leave a little bit before halfway through the game) does about zero plotwise, so don't worry about that aspect. When characters aren't in your party they're a bit slower to gain stats, but stats and skills are both easy to catch up on late in the game, so you're not doing yourself much harm leaving them there if you so choose. As for characters showing their character, Claudia's the soft-spoken, boring main, so, uh, there you go? If you play again, I recommend Albert, who has the best voice-acting (if you appreciate the quaver of a young, untested, and thoroughly righteous nobleman).
Unsolicited advice: stay away from Katanas, Clubs, & Spears. Especially Katanas.
