Turbo compresses data at an Opera server to make it lighter for a user that either have a physically slow connection or a traffic limit.
When your speed is decent, it won't make a difference. If you're on a rather high speed connection, it might even take extra time to push your data back'n'forth.
The video click-to-play condition is default with Turbo because such content takes on your bandwidth rather unchangeably. The feature compresses images and some other stuff, but I doubt it could take on a streaming content.