What influences a scene or not needs to be evaluated. If a geometry is not "water-tight", but contains for the camera invisible objects, doesn't mean that Global Illumination rays might not enter the Item anyway. Just to provide a hint aht it is not always a simple not seen by camera case.

Yes, if it has no influece to the scenetake it out. But if that becomes a lot of managment on the artist side, it needs to be evaluated.

My firm believe is, based on nearly two decades mentoring artists, that not optimized models or textures and rendering parameter are more the problem than a few objects left in the scene. All in all this is a longer them, and to be honest, I have currently time off, so I would love to push this into a Maxon Show as a longer discussion.

All the best