First video is quite interesting and... almost good. Almost, because tennis players do not work as 5 stage rocket. There are many more stages and the process of energy generation is more complicated.
There is also bad physics and biomechanics in this movie. I'm talking about this 16x multipier. Totally not true. I'm sure I can serve without moving my hips and the speed of the ball will be over 120-130 kph. So, does it mean that if I add 20 kph to my hips (quite easy to do, do the math), my serves will be 120 + 16*20 = 440 kph?
Also, all those angles look very magical, but in reality, what we are talking about? We are talking about place for motion. The larger angle means that there is more way and more time to accelerate, that's all. This is obvious at every joint in our body, at every stroke. Fundamental tennis rule: make place for the motion (btw the next rule is: if you don't want to be injured, remember about place where you can dissipate your energy...).
Hips are important, that's true. Why? Because you can use them to rotate the axis of upper arm rotation (the main source of energy at serves) around the main vertical axis of the body. This adds energy. But not too much.
At serves, there are many other sources of energy too. As example, you can decrease distance between shoulders. Or you can bend your whole body just before contact (that's typical for Federer).
"But certainly, hip rotation is a significant contributor the force of the serve, as is pronation" - please, not "pronation"
Have no time to watch other videos, maybe later.
There is also one very important thing in your post. You are not quite precise when you talk about adding energies and 5 stage racquet.
It's time for magic.