Construct 2 already spritesheets everything on export so the question of what you do in the editor is pretty irrelevant. FWIW, when I was developing the spritesheet feature, I could not measure any performance impact either way with using no spritesheets, per-object spritesheets, or large global spritesheets, so as far as I am aware it makes absolutely no difference at all, which is unsurprising since questions like this are often a waste of time.
So there is practicaly no performance gain when i aim towards a "one or two texture overal graphics" on my mobile game. Currently my enemies for example have their own spritesheets and are not part of a bigger texture. Also my ground tiles are all in separate texture. Did i understood it correctly?