I might be able to answer a few of your questions..............
Fast angle wheel sets should have no bearing as to the operation of the Kadee couplers.
If you have easements on your O-36 curves, you should have no problems with your trains going through them. If not, there could be problems. But the closer the trucks are to the ends of the cars, the better off you will be. The shorter your locos and freight cars are, the better off you will be. Coupling and uncoupling will work their very best on straight stretches of track. Start throwing curved track into the equation however, and coupling/uncoupling success starts going downhill in a big hurry.
My observations are based on a lot of experience with N-scale Micro-Trains couplers, and I have no doubt that my experiences would hold true for any of the scales. That being said, I have not tried Kadee couplers on O-scale as of yet. O-scalers with actual experience can chime in and add even more yet to this.
Hope this helps. 
