Maybe lets start from the beging.
A romance is a relationship between two people who are in love with each other but who are not married to each other. ... Romance refers to the actions and feelings of people who are in love, especially behaviour which is very caring or affectionate.
We do not have a romance or anything like that in EA BG3, call it buy its name, one night stand, hock up, casual sex.
I see no curting, no flirting, no interaction to initate a "romance"
Just a question do you want to bang? Yes? no? please fill check mark.
Shadowheart has a few dialogue options before the party scene that are flirty in nature and her party scene is not a "do you want to bang?" one. You just chat/flirt under the moonlight while drinking wine and can end it with a kiss. You can also lock yourself out of it depending on certain things you do in the storyline.
Gale's romance start with a courting scene not related to the main quest (not sure how to trigger it). Without that scene, he's not an option at the party.
Lae'zel, Wyll and Astarion are horny bunnies. Wyll even hits on both Lae'zel and Shadowheart in party banter...and Shadowheart is not impressed.
