I experienced the wonky romance implementation both ways. Some, like Lae'zel and (especially) Halsin went from 0-100 in the blink of an eye, which was very annoying.
However, I also got permanently friendzoned by Karlach, Wyll and Astarion because I didn't take enough Long Rests in Act 1, so important character moments with those three never happened for me. I've heard Wyll invites you to dance, but I never got that, nor the night time creeping from Astarion. These moments seem to be required, because I've been locked out of all relationship progression with those three characters. I'm at the end of Act 3 now and they've not had much to say since the start of Act 2 . Hopefully this has or will be fixed, though.
"You smell like battle. I can smell the blood and sweat all over you. I saw you massacre those goblin children and tear their heads off. I want you to fuck me here and now."
My Wyll danced with me near the end of Act 2, as well. The next night Gale got all emo and wanted to watch the stars with me. Y'all are too late I'm a Shart main