Watching the video, the preference is stated for active hi, but the green checkmarks shown are in the active lo box - implying to me at least the ACTIVE LO is selected.I would think a red x in the active lo box meant it was not selected. (Using GEcko 540 driver and trying to finish my setup)

Basically Active Low/High refers to polarity and the state in which a switch is in to trigger in Mach.  Some people will set their limit/home switches to always have signal runing through them when the swicth is triggered it disengages the signal and tells Mach -"I've been triggered".  This is the most preferable way because if a problem arises with your switch (i.e. bad switch) you will be made aware since Mach will trigger a reset.  This method is called Active High (I think)

Other People will set p their switches with the traditional lightbulb method-i.e. power comes to the switch and sits there until the switch is engaged.  When the switch is engaged it will send that signal to Mach and say "I've been triggered".  This is Active Low.

In other words, in One scenario a LACK of power causes a trigger, in the other scenario an introduction of Power causes a trigger.  Mach is capable of runing either way- it's the user's choice BUT... Active High is more commonly used AND safer!!!

HTH,
Sid