Personally, I really enjoyed Astarion’s story arc when playing a chaotic good character willing to support him, so I would strongly recommend not ruling out bringing him along in a good party. Popping a brief précis in spoilers below, both because it is a spoiler and also a bit off topic:
My PC slept with him at the party, then backed off sharpish when he was clearly trying to use sex to manipulate her afterwards. The fact he’d then in Act 2 recognise my PC was trying to do the right thing, albeit in the context of again trying to manipulate her, was for me one of the nicest bits of reactivity in the game that helped feel my PC present in the world (something that can be lacking). The way he started coming round after my PC supported his right to self-determination against Araj I felt was plausible and moving, and the way he broke down when choosing to reject ascension honestly had me a bit weepy. And at the end, he elects to live a life of helping people, albeit with a distinctively Astarion twist, so it feels that the net impact on the world of supporting him is a good one. And though unfortunately I only know that because I reloaded with a different choice at the end to experience the epilogue gathering, I found it satisfying that though my PC didn’t survive their adventure, their friendship with Astarion had helped him towards a good, fulfilling life, and the story that got him there was the sort of twisty tale that floats my boat.
Plus, while there some possible exceptions when following certain paths or if certain rolls are failed (eg when meeting Gandrel before Astarion’s nature is revealed), I personally didn’t find that as a good character there was ever a compelling enough justification for actually killing him, given that, for me, summary, extra-judicial execution when there is no clear and imminent requirement to prevent significant harm or loss of life is no part of being good!
But while, given the choices and rolls in my good playthroughs, Astarion didn’t do anything particularly heinous, I know he can be dodgy. And while I don’t recall feeling that there were important missing opportunities to challenge Astarion specifically, I’m sure there are gaps in particular scenarios, as I’ve come across a number of instances across the game in general where I’ve not been happy with the available options for dialogue or action. Some of those probably do reflect the writers’ preconceptions of what the player might be thinking at that point, but I’ve never actually felt gaslit or as though the game wasn’t allowing me to make up my own mind about what I was seeing. And given the size and complexity of the game, I’m generally willing to headcanon a suitable response where the game doesn’t give me one, though I’ve tended to report as a bug/feedback when there’s been absolutely no way in the game to reflect a reaction that I’ve felt was significant to how the story plays out.
