Construct2 only exports HTML5 application at the moment.
So no, you won't be able to make an exe out of a C2 project for now.
For the question about graphical terms...
C2 does not support shaders like CC does for example. So it makes it harder/trickier to apply some effects to your game, you have to "cheat" with assets and events.
I haven't played Limbo, so I don't know exactly what's the amount of graphical treatment applied, from what I saw in trailers it sounds like main sprites are black silhouettes, and there is some fog effect at time (you can emulate it playing with the opacity of some sprites).
I'd say it is possible to reproduce something similar in C2.
To sum up on your question is C2 more powerful than classic, on the strict numbers (according to this article from a few monthes back (figures have changed for the browser now I believe)) CC can display more objects than C2.
That said, the amount of objects that C2 can display is already more than enough to have a nice eye-candy game.
Be sure to check the arcade to see examples of games made with C2. What you see is what is posible, but certainly not the limit yet.