If you're speaking about what will be utilized in the DCT i30N; the new automatic that will be utilized in the Veloster N and i30N, will be a wet clutch setup. A completely new unit, not shared or utilized in any other Hyundai.
The current unit which is shared by most of the 2.0/T and below Hyundai's is; a DCT dry dual clutch setup and a standard converter unit. They are robust for use in the 2.0 theta engine and below. It's not adequate for anything above a 2.0 theta engine.
CVTs are the most efficient ones, yes. That's why Toyota also uses them in basically all of their hybrid cars. Problem with them is however that they will always try and keep the engine at optimal RPM for the currently desired driving style.
When you accelerate hard, the RPM goes up and stays there, kinda lika a moped. Problem with CVTs is that they are expensive and complicated to maintain, because of the way they're built: