Handycam 3D camera plugin?

The Comp Camera looks at all 3D layers. That is why it is there. It mimics a camera in the real world. You can add additional cameras and cut between them (not a very good idea), but it makes no sense to try and have two different camera views simultaneously in the same comp.

If you want to move some of the 3D layers around, add a 3D null and parent the layers you want to move to the null, then move the null. That is how you arrange multiple set pieces (3D layers) in the real world, and that is how you should do it in After Effects.

The only other option, (this is not a recommended option) would be to duplicate your comp camera, select the duplicate camera and the 3D layers you want to isolate, then pre-compose, open the Pre-comp and move the camera around. You will also have to duplicate any lights in the main comp, and you cannot collapse transformations. That suggestion is a bad amateur idea that can cause many problems. You end up with a 2D layer in the main comp. If you make it 3D and move it around, you lose all relationships to the other 3D layers, and if you Collapse Transformations, all of the lights and the camera moves in the nested comp (Pre-comp) will get ignored.