Making a rigable robot I am a complete Newbie in regards of rigging and animating, trying to create a Robot, which I will try to rig and move afterwards. 
I have two questions while I am at the beginning to avoid double work in the long run. 

Question 1:
Right now I have every part as a separate object, should I combine them to one sinle object for the whole Character? Because then I ask myself how the movement of the jaw you see in the picture should look like.



Question 2:
I want to make the neck, and probably arms and legs as you can see in the following link:
Make Bezier Curve look like Torus Array

I ask myself if I should use a torus array for this or rather a cylinder and try to achieve a similar look and avoid any problems of being unable to move the parts without any sort of unwanted deformation. 

Thank you all a lot. :)
Unless you have good reasons to keep some meshes separate (like a modifier that must not affect the other meshes), it would be simpler to join them.

For the second question, it really depends on what you want, it will deform but it won't necessarily be a problem so you should try this solution, on this topic you can follow this very simple tutorial by AgenZasBrothers that explains how to create robot limbs with Array and Curve modifiers, maybe at the end parent the vertices to bones so that you can always come back to a Rest pose.

Also maybe this answer I gave on how to rig a cartoon-like limb may interest you.