Hey there ,
I would be careful about deleting things that the engine is generating automagically, untill you know what they are. It would probably be best if you posted exactly what was being created, and if it’s a good idea as to whether it’s deleted or not. The other thing is this, if you don’t see them in the outliner, when in the editor, and they appear only when your running the game. You probably don’t have the option to actually delete the “actors/objects” anyway, as the engine is probably creating them, because either it needs them, or you need them for what your doing.
Whether or not a actor is rendered depends on whether there are actual components attached to that actor to render. If there is no components attached to the actor, there is nothing to render.
Hope this helps.