I really don't think the camera size has any effect whatsoever. Scaling everything up does make the camera field seem smaller, but this can be countered by adjusting the Z depth limits in scene mode. So, if you scale EVERYTHING up, including the Z-near setting and distance between camera and elements, the final render will be identical.
In a side note, be careful when scaling in scene mode. If you have an animated element acting as a parent of another element, and you rescale the parent element and it's motion path, the position controller for the child element(s) do NOT scale, but remain the same. This can have some very weird effects. For example, lets say you have a car with emissive headlights, and you place a pair of spot light in front of each headlight. Since you want the car to move around the scene, you make the car element the parent of the lights in the position and orientation fields. If you resize the car element in scene mode, the lights will move as if the car and its position path have not changed, and will not track with the car correctly.
Wherever possible, I strongly recommend getting your sizes correct (relatively speaking) in object and figure mode. If you want to use objects and figures at different sizes in scene mode, remember that you can import objects and figures from the current project, and Anim8or gives you the opportunity to give the imported copies new names.