I personally don't think the mechanics work that well or are very well thought out. This mainly due to 4 factors which, all together, just make the romances seem really forced, as well as annoying and unbearable sometimes. With maybe 1 exception that I know of out of the 9 companions:

• All companions are bisexual

• All companions are attracted to the player

• When attracted to the player they will all actively make a move on the player, instead of waiting for the player to chose to hit on one of them

• The dialogue trees are way too heavy on romance, to the point that sometimes the only friendly options seem way too intimate and even flirty.

Just 2 of those would be fine, maybe 3, but 4 really pushes it.

Part of what I mean by friendly options seeming way too intimate, is that instead of the game giving you friendly and obviously romantic options, it often seems to compress all of that into just one option (or just one way that the character acts) which skirts the line between friendly and flirty so as to try and retain plausible deniability ("I'm not interested in that character") while still giving you a way to role-play the romance ("That was clearly flirting/an intimate romantic moment").

Don't even get me started on Gale. His affinity was over 80 before Act I was over, and at one point I had four dialogue options out of which only one didn't seem flirty (the one I chose). Then, after he said we were friends, I had three choices "I want to be more than friends / We're not friends / That depends, what do you like about me?". Out of those, the third one is the one I went with, but even that seems a bit flirty to me. Then later he says he needs to talk to me "urgently", so my character goes to him, sits quite close to him in a way I would consider intimate and more than friendly, and he then professes his love for me.

Other than Gale: Shadowheart was quite easy to romance; Lae'zel said she liked my sweat or something; Wyll I've definitely had more-than-friendly conversations with; Astarion, simply due to his personality, has been hitting on the entire time despite me barely using him*. Halsin I don't use, Minthara is FUBAR, and I think Jaheira cannot be romanced. Karlach might be the only one I've used that hasn't hit on me yet.

*And I wouldn't even mind Astarian's personality if it wasn't for everything else.