Damn, Triss is Bi? That might make the decision easier for me! LOL. Just kidding.
I played all the games, but I only read the Last Wish, so it's a tough choice for me. I haven't done the Triss quests in Novigrad or the first Skellige quest in TW3 on purpose. I'm avoiding the decision for as long as possible, but I'm running out of quests to do. Haha! Also, I'm waiting the patch to fix the glitch in the romance dialogue choice in Triss' quest where you get "locked in."
But you, as the player, should pick who you want. It's your game, your Geralt. Don't worry about "canon" or books vs. games. That will drive you nuts, as it does me. I must admit though, the flame wars are quite amusing between the 2 camps. I'm here on the sideline enjoying it very much.