The first run as a sorcerer was with Shart, Astarion and Karlach, second as a moon druid with evil Shart, Minthara and Gale.

I try to have a balanced team with aoe and single target focussed characters, enough frontliners to tank the damage, healing and support, and utility such as lockpicking, sneak and talk to animals and the dead. And I definitely don't respec companions to something else entirely, because I like to think of them as existing characters that can't just change who they have been up until now.

I do switch characters for quests from time to time, but in hindsight I wish I didn't. The 2nd run with Gale for example would have been much better if I wouldn't have known most of his quest interactions already! I'll definitely change that for my next RPG, not being too greedy on the first playthrough.