As far as my XP37 Xtra goes, i adjust my picture height and size for every resolution and the monitor retains these settings in its memory. I lower vertical size for 16:9 resolutions and lower picture width until i have full raster. I did this for each resolution so i dont have to touch it. When i change resolution, width, vertical height changes accordingly, giving me black bars for 16:9 resolutions and full screen for 4:3.
Of course, if i want full screen in 16:9 resolutions i can put vertical height higher and while it distorts a bit (objects are slimmer) this is not an issue in most games. For movies i return the vertical height to normal. Also, when i play blu-rays, the new movies are often even more wide-screen (2.33:1 if i remember well) so i augment vertical width and horizontal size accordinly to make it 16:9. Of course i lose some information but picture quality is not lost since this is not a digital zoom but just a stretch of width and height of the raster.