I think in C2 we will let you have objects in the object bar with no instances actually placed on a layout.
Wooo!
About efficiency, I've had to do both. In one case I needed 4 objects to always be together. If you place them individually they might not be at the right position (image point and matching angle) and doing so in the editor is slow and overkill. What I did was use one object (the most visual one) as a placement marker and then on startup destroy the other 3 instances then for each one of the markers destroy it and recreate it at the same spot. Since the other objects were in a container they spawn as well (that saved 3 actions) and then you gotta place each one of them.
So yeah, sometimes you'll have to place them with events. Most of the time, not.