1: The former. Launch zone changes with closing velocity, altitude and the like. Basically the missile physics are modelled in the same way as the missile AFM in DCS world. (I know some of you may find that hard to believe that but its true. It all boils down to controlling the 6DOF velocities of the missile and SimConnect provides the means to do just that for any object in FSX).
2: Yes, yes, yes, and yes