Clutchbone - successful use of the PID instruction requires that you have some basic knowledge of the action of a PID loop and the parameters which control it. If the concept of a PID loop (it is internal to the stand alone controllers you mentioned) is new to you I suggest you do some research.
Your rung 18, which we advised you to delete, is a crude attempt at temperature control.
If you used just it, without the PID rung, you could have had a MATH block at the end to move some value into Platen Heat 1. This value would have to be enough to raise the temperature to the setpoint. Actually it would probably be better if it was a bit higher than that.
You would also would have needed a rung which, if the temperature was greater than the setpoint to trigger a math block to move a lower number, even 0, into Platen Heat 1.
This would provide a very crude control of the temperature much like your basic home temperature control thermostat.
A PID attempts to provide a much more controlled response which ends up maintaining the temperature very precisely at the setpoint.
Imagine controlling the temperature yourself, watching the readout from the thermocouple and adjusting a potentiometer to vary the amount of heat from the heater. After a while you would find yourself developing strategies like 'full on' at the start but slowly tapering off the control as the temperature approached the setpoint to prevent overshoot. You might find yourself tweaking the potentiometer slightly from time to time if the temperature drifted from the setpoint. These are the type of things the PID loop does if properly tuned.