I'm not a fan of video 2, I like the idea of explanation parts being the focus. If I wanted quick model solutions, I doubt I'd go look for a video - I'd just load up the assessor report or iTute solutions.
Whether I like the idea of video 1 or video 3 better though, I can't decide. The longer explanation of video 1 was neat, going through and explaining the chain rule etc. That'd be the kind of stuff I'd be looking for at the start of the year, learning the concepts in the first place.
Video 3 was pretty compact, if I was stuck on a particular question during exam prep and went to go look up help, I might prefer the style of this video.
Oh and also, for Exam 2 questions, showing how to use the CAS (and any neat tricks for that particular question) I reckon would be pretty handy. I'm not sure how you would go about that though (with different CAS's being used etc.). I guess something similar to what KhanAcademy does with calculators, using the software.