I'm running X-Plane at 1366 x 766 in full screen mode. Here are my settings:
Flying a pattern at a very demanding add on airport my fps never dropped below 35. XP9 is very easy on todays medium hardware. One little correction, there's a little typo in the description of my notebook, it's 4GB Ram, not 8.
Two screenies from that test flight, so you can have a look how everything was displayed.