To clear up a few of the questions:
1- We try to balance the AI as much as possible so theyre consistent track-to-track, car-to-car, so that if for example you´re a 100% strentgh level driver, that will be your setting throughout. It´s a hard balance to reach though and there certainly are some inconsistencies still.
One of the reasons it´s a tricky challenge however is that it´s hard to pinpoint where the inconsistencies are from the AI performance itself, and where it is from the player himself being inconsistent - faster on given tracks or given cars than in others. In this case it could be AI performance is indeed off at Campo Grande, but it could also be you need to practice more / find a better setup in that track. It requires a lot of collective testing to figure that out so the more feedback we gather, the easier it is to pinpoint where there might still be problems.
2- The collision "warping" issue on wheel-to-wheel contact is probably related to the simplified collision model for the wheels, Not much can be done there.
3- The AI physics is for the most part same as the player´s, except for some AI-specific multipliers & simplified models for tires in particular, both for the sake of performance as well as balancing / stabilizing AI driving.