This is the way how I see a LSD diff
The preload thing are basically springs pushing 2 plates together, and you can adjust the force of the springs. If the difference of torque between the right and left wheel is smaller then the preload setting, it behaves like a locked diff. If there is a difference in torque of both wheels, and it is higher then the preload setting, the clutches start to slip.
The amount of slip allowed is limited by the power locking and coast locking. If the power lock is 80%, then there is only a 20% difference of torque is allowed between the wheels. I think you can figure out the coast story too.
Power lock and coast lock are only in working if the torque is higher then the preload.
Please correct me if I'm wrong, but this is how I kinda understood it from this topic.