So yes you will be using your storage here or there. These have to go somewhere unless you are using a streaming service like Netflix. http://www.cnn.com/2013/06/10/tech/web/itunes-radio-apple-wwdc/ notes that Apple was late to the streaming no local storage game.

The Apple TV however changes how this works. If you don't download them on the laptop, then it's not on that machine. As to the cloud, I may shortchange you on how that works. Rather than copy the entire gigabytes to your account, the real way it should work is that it notes you have access to the video and the actual storage is in their cloud space. Netlix is like that.
Bob