Defrost strategy

So i'm slowly figuring out the HVAC system on the v, and as a result, the most efficient strategy to defrost/defog the windows. I love the auto climate control system, just one less thing to fiddle with while driving, set it and forget it.

Anyway, I was initially a bit concerned about how defrost/defog would work on this type of system, being different from the manual systems i've had in previous cars.

I was thinking i would have to turn off auto and use manual controls to keep the windows clear and keep the cabin comfortable, but so far has not been the case. Will have to see when it actually gets colder out.

Temps have not gone much below 32f the past few days but i've noticed with auto on it will sometimes switch vents over to "defrost and feet" as opposed to "feet" most of the time.I did learn something, to my surprise, by reading the manual that when vent function is on feet only it actually blows air towards the windshield as well. Not sure then how "feet only" differs from "feet/defrost". Does feet/defrost also use AC to help defog?

Does the system automatically detect humidity levels and turn it to defrost sometimes? Does outside temperature factor into the climate control decision making? it seems kind of random to me when it does this, though i'm sure there must be a reason why on its own it decides to blow more air towards the windshield sometimes as opposed to the feet.

With this in mind my strategy so far has been to leave it on auto at 23c(74f) and occasionally when the windows need some extra defrost help, or things start to fog up bad, i hit the front defrost button. Once everything is defrosted I hit the button again and it goes back to my previous setting (auto at 23c).
the front defrost function does seem to use a lot more juice though as i noticed the engine will usually start up when i press it if i was in EV at the time.

So when using defrost function even when the AC light is not illuminated does it automatically activate the AC to help dehumidify the air? I know in my old car with manual hvac controls, the AC always came on when control was set to defrost setting on the windshield even though the ac light was not illuminated.