Well it depends on what style of riding you want to do. width and drag are less important for park riders and more important for freeride/all-mountain.
Size 11 is borderline and all boards are a little different. Waist width is a measurement of the narrowest point of the board so two boards with identical waist width but a varying sidecut radius will be different because of where you place the bindings relative to the edge. Some overhang is ok and won't kill you, generally the most you should hang off the edge is 1 inch.