I recently beat Tex Murphy 1&2 and both those games required specific conversation selections otherwise you could dead end the game. Is Under a Killing Moon similar or can I can choose whatever topic? Thanks

There are a couple of places in the game where you have to select a certain response option to proceed (otherwise it will end your game, I remember being frustrated as I hadn't saved for a while at one point). Beyond that, I believe there is only one ending for the game and your path is basically linear no matter what option you chose.

I wasn't until the next game in the series (Pandora Directive) that responses actually branched the story and led to different endings.