Arduino-CNC sheild based controllers for K40

I do not use an Arduino and shield for control on my K40, rather smoothie running smoothieware.

I get questions on how to interface an arduino-shield to the LPS.
So I am trying to get more informed on this setup so that I can provide accurate help.

What I learned from research is that when using an Arduino and sheild:

  • Laser Mode must be enabled in GRBL
  • The Arduino pin D11 is used for PWM output and is HIGH true
  • M3 & M4 gcodes enable the laser
  • Laser power is controlled via the S parameter

For those of you using Arduino-sheild-grbl for controlling a K40, can you tell me if the above are correct?
Is D11 always the Arduino port that is used for PWM control?