The only character who I haven't been able to progress a "relationship" with while playing a goodie two-shoes is Shadowheart...and she's literally a devout worshipper of Shar.
Gale is generally pretty neutral, though upbeat and nice enough. Wyll is a genuinely good person. Astarion is a vampire, sure, but he's also never been out in the world as a vampire with any control over his actions; a massive fish out of water and I think they've done a pretty good job of showing that. I feel like Fae'zel's character could definitely swing more to the good than she currently seems to be as she has to deal with more of Faerun, especially with how her interaction with other Gith goes in the early access.
Yeah, sometimes you get -rep with companions for being good. So far this isn't really blocking anything for a good character. It does, however, almost immediately hardblock Wyll if you decide to be evil.