I really enjoyed Shadowheart a lot and she was my favorite, I loved her story I think it was the best storyline in the whole game and one of my favorite companion stories in any RPG.
I liked Astarion more than I thought, and his questline was pretty okay I liked the climax at least.

Wyll and Gale were meant to be my '' magic buddies '' since I played a Warlock, but I felt like the game was reaaaally trying to push me into romantic moments with them and that I had to break their feelings ( I was romancing Shadowheart ).
My favorite thing about Wyll ended up being Mizora.

Lae'zel I didn't like on a personal level, but I thought her writing was very immersive so I kept her around, I also appreciate that she wasn't stupid and could see reason in spite of her devotion to her people.
Which is also why I reaaally didn't like Karlach at all because I felt like her writing came across like a Tumblr DnD OC, she had way too modern writing that was trying too hard to be '' badass '' imo no actual real person behaves and talks like that and it's not an in-setting thing.
If anything I think with her background her personality makes less sense.

Ngl the new ending for her just further cemented that for me, it just felt like fanservice rather than good writing.
Just my opinion ofc I know it's heresy to some not to like her...
But she's the only character I actively disliked, maybe I am old and grumpy but adults talking and acting like teenagers isn't endearing to me it's just weird.

No idea about Minthara because I just recently started my evil playthrough to get her after she was finally fixed.
I love her voice acting tho she sounds more '' mature '' than usual.
I don't mean like a grandma xD, but I dunno what other word to describe it she has a very unique voice and way of talking I really love.
I can't think of another character that has a voice like that there's just something about it I find really appealing.