Settings are exposed as standard public properties in VPVehicleController, and settings classes are decorated as [Serializable]. You may access these properties as with any other standard property in Unity and serialize / deserialize them using any of the regular methods available in Unity / C#.
Reference: properties exposed in VPVehicleController
Note that some of these settings include references to other GameObjects in the vehicle. For example this is the case of the VPAxle class, which includes references to the VPWheelCollider components. Serializing the VPAxle class stores the references but not the actual settings of the wheel colliders (which also include references to the visual GameObjects of the wheel).
A good practice is defining a subset of properties that may be configured outside the game, leaving the other properties as per-design in the vehicle. Then save/load those properties only from an external file.