Have bi-wings been used without creating more drag?
Moving the wings vertically apart would mean more and heavier supporting structure, but also a higher pitch moment of inertia. Since this grows with the square of the vertical expansion, a biplane with a lot of distance between both wings will be hard to control and very sluggish.

The real advantage of a biplane is reduced induced drag because less structure needs to be lifted. When cross-bracing enables the top wing to work as the compression member and the bottom wing to work as the tension member of a truss, a very lightweight structure becomes possible, especially when the size of the aircraft grows.

If all you have to power your airplane is a heavy, inefficient piston engine like those at the beginning of the last century, and you can tolerate that your aircraft won't fly fast or far, a biplane is indeed the lowest-drag solution.