Thanks for the kind words!
Each projectile is instantiated as a seperate object. There is no sophisticated physics simulation for the projectiles; their position just follows a ballistic curve, so nothing computation heavy here. Of course the units have to aim correctly to hit the moving targets while considering a ballistic curve (more details on that here), but this is calculated for each weapon before firing, not for each MG round currently in the air, so that is still ok.
The homing missiles however have a basic AI in-flight as they have to hit a moving target while avoiding obstacles. So with a lot of anti-armor units, the framerate will drop unfortunately.