Can I record player's choices to "an outside source which controls the game mechanics"?

As others have said, INSIDE ChoiceScript you can track hundreds of variables, but it’s all contained inside each player’s “bottle” i.e. not in contact with other players/external data.

If that is something you want to do, look into tools like DialogFlow that are marketed as being for “chatbots” but are actually just CYOA set-ups with a lot of more flexibility. For instance you could make a game where TWO human players compete head-to-head, but not in ChoiceScript.