Overall the serves are very good.
About the second set of videos, putting the radar gun at the service line will drop the speeds by at least 10mph.
For those people who want to know if you can serve 100mph, you can ask yourself these questions:
1. Is my motion smooth and relaxed?
2. Does the racquet drop all the way down when I start the swing?
3. Do I have good shoulder rotation?
4. Do I have good pronation?
If you can answer "yes" to all four questions and are male, then you should be able to serve 100mph with moderate effort. Now the problem is most recreational players just don't have all these components.
For a 100mph serve, the ball should hit the ground at about the same time the racquet bobs upward after the followthrough.