That photo is pretty close to how I imagined it (though remember that there's an issue of scale here, the chasms of the Plains are usually about 15-20 feet wide, not 50-100 feet as those in the photo appear to be), but I know there must be some height variation in the plateaus because Brandon describes them pushing the bridges across from higher to lower rims, and of course at some point we have the Tower.
I would say it's not quite as jagged and tilted as Whelan's cover, but not as flat as that photo reference... split the difference, and remember that they are the "shattered" "plains"... both words are operative descriptors, so while it's broad and flat(tish) the land is cracked and split... Brandon's original vision was of a broken dinner plate, if I recall correctly.
I would think that the breaks are more jagged, not so much the smooth and rounded curves that they are in natural formations carved by water. The Highstorms create flashfloods that do carve out the chasms somewhat more, but they do so violently rather than slowly over millenia. So again, somewhere split between smoothly carved canyons and jagged, shattered crockery.