You are partly right, when I train people I ask them to follow the extensive science of mirror and matching, if you are dealing with older professionals than a formal approach is good if you are dealing with whatssup kind of crowd than you use their vocabulary and style.
Depends on what your goal for the conversation is, maybe one wants to wife the subject, establish long term business partnership, develop a friendship than you cant really walk away. I dont really engage in Idle talk. Again the presenter of the video mentioned to focus on the goal of the conversation.