The 5D III AF adjustments have there own control panel now, they are not under the C Fn: tabs any more. I found quit a bit of information on the 5D III but couldn't find as much on the 1D X. No doubt the info is out there somewhere and I am going to keep looking.
I think your speculation is probably going to be correct. The 5D III will be excellent at one shot mode, and very good in AI. But the 1D X will be the star overall and will handle both one shot and AI mode the best.
With the price increase of the 5D III it may be Canon's idea that the 5D III is moving up to take the spot that a 1Ds used to occupy, as the best high resolution camera, and the 1D X replaces the 1D IV and is expanded to handle the high resolution work well. The question for me is going to be how well does the 1D X perform vs the 5D III when doing landscape, portrait and macro. Will the 5D III perform slightly better in those areas and fill a niche that the 1D X with its lower pixel count ( which we questioned early on).