The settings in IL2 don't change the flight model. They enable or disable things like engine overheat, pilot blackout, limited fuel, limited ammo, landings/takoffs or air spawns, maybe something about stalls/spins, and things like that. The overall handling of the planes is pretty much the same regardless of your settings.
On top of that, the overall handling of ALL planes is almost identical. They definitely use a single FM for the entire game, rather however AH does it.