In my design of the quite early, mid-21st century Bonaventure
, the warp drive is the ring combined with the domes at the front and back of the ship. They are roughly equivalent to the coils in a nacelle (the ring is one coil) and the domes on the front and back of the nacelle. The ship is like one, big simplified nacelle with a small habitation area inside.
The things that look
like nacelles are really the sublight drive. They are antimatter fusion rockets, so one could see how they might look kinda like nacelles. But they only look
like nacelles -- functionally, they are what on later ships would be the impulse drive.