How does C2 handle memory usage? Does it load all the layouts simultaneously? I have one layout where I put all the objects that need specific default settings and variables and it has become quite a mess. Is this a good way of handling stuff like this or should I set all those things at the moment of spawning objects? Also do I need to hide objects that aren't on screen seperately to save memory
As long as those objects are just editor-side that layout shouldn't cause any troubles for you, I think it will be the default values if they're the only instance of them/set before copies are made in other layouts.
Construct 2 also handles the rendering on/off screen stuff itself internally in a manner that will probably be more efficient than events, but you can do extra things like making sure WebGL FX are applied to whole layers instead of multiple individual objects that are supposed to have it.
However, as for making big games in general, I would say give these a read:
Those are posts from developers of two of the three big "dream" game examples on the scirra homepage ( http://www.scirra.com/ ), and I too have a game on Steam with a friend I met on the forums here ( http://store.steampowered.com/app/334190/ ), and loading time can be quite a while for large games exported to EXE with Node-Webkit, we also had troubles with updates to C2 and updates to Node-Webkit (but this part should be better now that you can downgrade any time at: https://www.scirra.com/nwjs , we are currently using 0.10.5 for the best experience but 0.12.x is looking promising).
Even so, it should be possible to make a game like the one you referenced above, not sure how it would run in anything other than Node-Webkit though.