Good tips on those online books my CT neighbor. Funny that the OP mentioned Landry as connected to Shotgun. Growing up as a Cowboys fan, I remember asking my Dad why is Staubach standing so far back from the line..? lol Good times.
I still run quite a bit of my offense from 12 or 21 personnel, but I couldn't possibly imagine doing this 100% of the time.
Different strokes for different folks. There are NFL coaches right now, McVay comes to immediate mind, that run very few packages, but do a great job of mixing plenty of concepts from them. All different ways to approach it, depending on one's own philosophy.