How Many Cameras?
If there's only ONE camera, in many ways, things are simpler and easier .One video cable between the camera and the audience's video display and one camera operator focusing on one thing - getting The Best Shot. But to get The Best Shot the camera and operator have to move around. If the camera operator is focusing on the On Camera display - he/she can miss seeing - the demonstrator's head, anoverhead light - and maybe getting the videocable from the camera hung up on something - or tripped on.
Ideally, it would be nice to have a tailstock end camera, an overhead camera, a headstock camera, a front wide shot camera and a roving camera on a dollied tripod, maybe even an overhead boom camera on a dollied tripod. BUT - the more cameras, especially cameras that move, requires more people to operate them, more wires and cables and more stuff to set up, take down and more stuff to store (and possibly lose). Then there's the distractig effect sof lots of cameras and operators around the demostration area and the obstruction of the audience's view of the demonstrator.
At minimum, TWO video cameras are needed - one overhead, one tailstock end "end view".
It's that Overhead Camera that presents a "challenge".
If it's moveable it can distract both the demonstrator as well as the demonstrator's audience, or get in the deomostrator's way. If there are overhead lights, it can hit them or has to be maneuvered around them.