I've only ever played like, Skyrim, so my thoughts on the romance were like— It'd be like that, very light, not much 'romance', but I just now got Astarion to 40 and the confession dialogue comes on so strong, lol. 

We haven't killed all three goblin leaders yet. 

If I reject him at 40, will I still be able to start a romance with him at the party / Act 2? Also, does the dialogue ever get toned down with Astarion? Or does he come on this strong for the rest of the game? 

Also, is it worth it to romance him? Like, if I choose to stay just as friends with him, will I still get his full storyline? 