That answher is still not near to complete.
Got to start with the difference between 'system > create' and 'sprite spawn'.
Create just creates a sprite in a given position with the same angle as the first made instance in the layout.
Spawn creates a sprite at a given position and aligns the newly made sprite with the angle of the spawing sprite.
A turret 'spawns'.
So, using 'system create' you have to Set angle of motion (or the angle) towards a target, using one of the above methods. And you can steer the bullet on its way using same methods.
Using spawn, you can rotate the spawner towards the target, using one of the above methods. And you can steer the bullet during its way using same methods.
Right, now i hope it stands.