You hit the nail on the head regarding the latter two returning companions.
The playable pair were definitely better but I was still disappointed with how they were implemented.
Jaheira was by far the best of the four. She had the same sarcastic, tough-as-nails, but caring personality I remember and I appreciated all of her interactions in the city. My main gripe is that she joins your party as a level 7 adventurer. Last I remember of her, she was fighting near-Gods with me in Throne of Bhaal. Maybe one can wave hands and just say "well she's old now" but it felt pretty immersion-breaking for me. She can also die really easily in the Moonrise attack if you don't ask to recruit her for the fight (which can be a pretty reasonable thing to do without realizing, if you don't want to mess up your current party comp), which is a disappointing end to the character.
Minsc however was not at all fleshed out as much as Jaheira was, with minimal dialogue, no real quests, and an appearance so late in the game that you barely get to know him. He felt more like a tacked on cameo. And he was also given... a 12 in strength, when his enormous strength in the originals was a hallmark of his character! That doesn't seem like the guy who tore the bars apart with his bare hands in Irenicus' dungeon. I always built him in the heaviest armour you could find and slapped on a two-handed sword or halberd to smack his enemies, but that just doesn't make sense here anymore. Meanwhile he was also given a 15 in wisdom... his lowest stat in the originals (at 6), which made perfect sense for his character. No one should ever describe MInsc as wise, yet here we are. It felt like Larian just saw that his original class was a "ranger", gave him ranger stats, and didn't think about it further at all. This wasn't the Minsc I remember.
But perhaps the most disappointing thing is what happens if you don't recruit Jaheira in Act 2. When you find Minsc in Act 3 you have no way to snap him out of his delusions and you are forced to kill him and watch Boo mourn his dead body. It's one of the biggest slaps in the face for a character's ending.
