Given that the Romulans are an offshoot from the Vulcans, and also given that the Vulcans use rings as their warp nacelles, could this explain the double-wing design of the Romulan warbird?
If the top and bottom of the wing make a ring, could this be the warp nacelle?
The inhabited parts of the ship could be the beak at the front, the horseshoe at the back and the connecting structure that goes between. The entire wing, top and bottom, could be the wrap-around warp nacelle. The actual pods at the wing tips could be a part of the warp system, or maybe just the impulse engines.