This is all academical as resolutions bigger than 800x600 simply aren't possible yet on a technical level. If the plus code ever supports resolutions higher than that, you can be sure that all resolutions up to JJ2+'s limit supported by your monitor will be supported by JJ2+ as well. That probably includes 1280x720. Until then, use one of the fullscreen widescreen resolutions if your PC supports them or play windowed 800x600.