The only thing I'm really for sure about on this topic would be using the AWD for launching off the line at a drag strip. At least that's how I've always heard the 4x4 diesel guys do it... LOL! As for the rest of your questions, I really can't say. Mine is 2wd so I definitely haven't had the pleasure of playing with the AWD option, but man I bet it would be a blast...
My line of thinking when I was going through the decision of the purchase was that if I had 4wd/AWD, I would've felt like it would be a waste to have it and not have all terrain or mud tires on it.... And THEN, if I were to have said all terrain or mudders on it, I would've felt like it was a waste to never take them off road... That being said, next thing ya know, I would've had a $50k+ truck in the mud every other weekend and that just wouldn't be a good thing for me. Fun? YES! Smart? Heeeeeeeell no..... LOL! I just aint got it (money) like that... Hopefully someone else can help ya with the rest of your questions tho! Good luck bro!
2012 F-150 Harley Davidson #3566 4x2
White Platinum Tri-Coat Metallic, K&N CAI w/ filter sock, SCT SF3 w/ custom tunes, Alpine audio processor, LockPick SYNC, JL Audio HD 900/5, JL Audio C5 6 1/2" coaxials in front, JL Audio C5 components front & rear, 2 JL Audio 13 1/2" TW5 subs in custom box, Weather Tech Digital mats front & rear