Servo vs. stepper for camera mount
I would recommend a stepper motor plus worm drive. You will be able to keep this perfectly still, which is what you want for a camera.

A servo motor contains a circuit which actively tries to maintain the position of the motor. This system can be affected by external forces, electrical noise from the angle sensor, and poor tuning of the control algorithm. All of these things can lead to instability of the motor position, unless you spend good money on the motor.

On the other hand, if you want a stepper motor to stay perfectly still, you just stop stepping it. It will hold its position very accurately, and the worm drive will prevent you being able to back-drive it.

The other benefit of stepper motors is that you generally don't need to measure the rotation. If you're using it within spec, then you can be fairly confident that it has moved the number of steps you asked it to. So confident that many CNC milling machines use stepper motors without any kind of position sensors, and can machine parts for hours without loosing steps.