I think the difference in the setups mostly involves the rear of the vehicle, as the Cobra has a negligible rear camber due to the solid axle. For the front, it makes some sense, as both a Focus ST and a Cobra are a bit nose heavy. The interesting thing to look into (to me at least) would be how the camber would change during travel; that would be a good look into how similar the front suspensions are set up, though that's not something that can really be tested without a lot of equipment, nor would it correlate to the game. After rolling several cars, I've noticed things such as IRS, solid axles, de dion axles, etc for rear and double and single control arm setups for front suspensions aren't exactly accounted for (and there is a lack of things like axle tramp on solid axle cars, also a good tell). Well, that, and it would add lots more work to the developer's plates to include that stuff.
On the Forza ST with real life settings, that makes sense, its pretty hard to find spring rates for certain cars. I also find it kind of annoying that Forza doesn't use actual stock spring rates for the cars, but I can understand why they don't.
For aero, that make a lot of sense; to be honest, tuning a car specifically for a track makes more sense to me than tuning for general use, its just something that takes more time than I'm willing to give usually, so I settle more often than not with a general tune.
Last (probably) question for general tuning stuff (next will probably be help with specific tunes, though as of right now I haven't had a setup that is too unruly), which steering wheel would you all recommend?