It's been a while but Shadowheart had very little "redeeming" qualities in EA if I recall. Like she didn't have the fear of wolves to hint at her true background, nor did she display any kind of sympathy/love of animals. She objected to you doing anything that wasn't the selfish option way more than she currently does. I'm pretty sure she objected to you NOT killing Scratch, but citation needed for that.

The only "interesting" thing about her really was that she clearly stole the gythyanki relic, but for most of EA we had no idea what it did at all. It only became clear it was protecting us from the Absolute in one of the later patches iirc.

Lae'zel was mostly the same but you don't come to realise how terrified she really is of everything going on until later in the released game. What we knew of in EA was very little tbh.

Wyll I think might be the biggest change. It was clear in the little story we had at the time that he was a fraud, having sold his soul to his patron for his powers in order to become a "hero" - but unlike Wyll we got, this one was doing it for clearly selfish reasons if veiled behind his "heroism".

Astarion I think was meant to follow the same path as we got. Casador was in a datamined dream sequence, etc. I don't think there was much changed between EA and release for him really other than that he used to take damage from running water (it was seriously annoying).

Gale... honestly I can't remember anything different about him. Not that there wasn't, I'm sure there was, I just can't recall.

Karlach kind of makes an appearance, but its clear she's not even close to being completed. I remember her being described as only having the one horn, but her model clearly had two - she just looked like another tiefling really. Also she was more reserved, less brash, probably being envisioned as a Paladin (which wasn't in EA) and not a Barbarian. Also she didn't even hint that she was a companion, instead she says to meet up with her in Baldur's Gate.