I would think 2 layers of frame would make it stronger than mitering. Two 1/2" layers will make up your 1" depth, make the edges overlap.
A jointer is a tool that shaves a narorw bit of wood off, kind of like sanding, just not as smooth and allot quicker, more like an electric hand plane. Remember, if you are building a 2 frames that cover 4 feet, you actually need the frames to be just smaller than 2 feet each, the fabric has a thickness that must be taken into account. Bud is building it to measured size, then shaving just a little off to take this into account.
Try looking way back in this thread, I think GPowers did the multiple layers overlapping, and has great pics of it all.