I don’t know about your frame rate change; it’s likely just changing because you’re changing the view and seeing different objects. If it’s dropping from 60 to 30, you probably have video sync on, which makes it difficult to come to meaningful conclusions about frame rate. Turn it off with:
sync-video 0in your Config.prc file, and you’ll probably see the frame rate drop from 65 to 55 instead or something more reasonable.
As to the difference between base.cam and base.camera, they exist as a convenience. base.cam is a child of base.camera, that’s the only difference. If you move base.camera, base.cam comes with it.
The reason they exist is so you can have multiple cameras attached to the same node (base.camera) and move them all as a unit, like for instance a front view and a rear-view mirror view or something. That’s why we recommend moving base.camera around whenever you want to move the camera, it gives you the power to do this.
If you move base.cam instead, though, nothing bad will happen to you. It certainly won’t have any negative effect on your frame rate. If you’re seeing a negative effect, it’s not because of this.
David