I am replaying wticher 1 right now and yea I don't see it. they seem like they hate each other and get on eachother's nerves. triss still seems desperate to be with geralt to me. lambert says he doesn't like triss when you ask him and thinks she's too pretentious. triss said it was horrible having lambert look after her after she was hurt in the opening battle and you give her the potion. I've not gotten to the part where she teleports you to her house in vizima yet but i'm pretty sure choices you make don't affect that either. for me at least this would also completely destroy triss' character and the romance between her and geralt because you are led to believe that she is completely enamored with geralt, and it plays as sort of a contrast to the toxic relationship between yen and geralt, which included them cheating on eachother, I think why a lot of players choose triss over yen, because the relationships are not portrayed the same, yet if triss was going behind geralts back then it would seem like a toxic relationship as well. I think it would destroy her character as well for a lot of other fans probably since it seems completely out of character for her to do this, at least at the beginning of witcher 1 when she's trying to get geralt to be with her, and if you use the books as a prequal to the games then she has been wanting to be with him for awhile, as you said.
...and the thing about there being a possibility they hooked up when geralt was presumed dead, also doesn't quite make sense, but that would probably be the best time if they were gonna have a fling. reason it doesn't make sense is because lambert says he jumped out of a window to evade being caught by a friend. assuming he meant triss was his lover there, and geralt was the friend, geralt would've had to show up a lot earlier, back from the dead, and knock on triss' house in vizima, where it is suggested the footsteps that are there belong to lambert. Then he would have to go back and disappear again, and come back from the dead to start the beginning of witcher 1.
Agree completely - for me, having read the books multiple times, the relationship CDPR presents with Triss & Geralt seems to be a much more legitimate relationship, at least in the terms I think of a relationship in, based on my own life experiences. I've played all the games about 6 times a piece and as mentioned earlier read the books a couple times, and as you described, the relationship between T&G just feels much more like a relationship should if you're looking for something healthy and monogamous versus something toxic where you're constantly fighting with your significant other, breaking up, and screwing other people, etc. As I play through the games, it's like a nice feeling with regard to the romance angle that, to me, it's like the romance angle is solid and unwavering, at no point during the games was I concerned that Triss was cheating with anybody else as she seemed to always want to be at Geralt's side. Even the description of Triss in Witcher 2 in the glossary describes that in detail which is the polar opposite of Yennefer, who seems to want to control Geralt and order him around like a little kid versus having an equal and loving relationship.
Had I seen some actual character growth from Yennefer in Witcher 3 I might have selected her, but she's just as insufferable in W3 as she was in the books and so I take great pleasure in kicking her to the curb every time I play the game.