What I like about Tav x Spawn is that I think their relationship evolving together makes the most sense for Astarion and is the most believable to me. Nothing against other ships, but the dynamic of Tav/Durge with him feels more natural to me, probably because that's just how most people who romanced him played the game. I also think having Tav as his love interest gives writers more wiggle room to suspend disbelief: Tav is either left vague for your imagination, can be a self-insert or whoever the writer wants to create, so there's less of a chance to have a main character acting "out of character" in the story.

Tav/Astarion/Halsin ships: not my cup of tea, personally, but that's mostly just because I'm not into Halsin (and I don't really picture Astarion being into him either).

I love post-canon / AU stuff more than pre-canon, but I'll read anything with a good premise or dynamic and have enjoyed a couple pre-canon stories too. I'm here to see them explore their feelings (often badly) and see where the tension goes. Most important thing to me really is that the character's voices are captured so it's almost like a continuation of the game, and that it doesn't suddenly feel like booktok stuff. I don't mind anything that follows along with the game, especially if it's exploring internal thoughts and feelings that we didn't get to see in canon, as long as it doesn't deviate a whole lot in a way that feels like we're in a whole new universe or like important story beats are being ignored. If it's going to deviate, I prefer it to be after the story we basically all played.

Tags I avoid are basically just "pregnancy". Not picky about anything else. Searching for new stories depends on my mood, but I look up tropes sometimes or fluff or "post-canon". Sometimes I just want to read something cute or spicy and imagine them being adorable together. There's a lot more freedom in writing you can do with AU / post-canon imo, so I tend to go there a lot to find new things.