Actually #1 is "largely" true but, like most things in this game, it's never 100% of the time.
Make-up does play a role in the recovery, at least the length of recovery, of a player. Medical plays a much larger role. Of course, there's no way to "prove" this without hundreds, if not thousands, of example. But, in my experience, the lower make-up players seem to be injured longer. Of course, there are varying degrees of "ankle, sprained" so you can obviously write it off as "Well, he took longer to recover because the injury was more severe" any time you choose.
Since I largely avoid low make-up prospects, I don't have an indisputable feel for how low make-up players decline. However, I'm pretty damn sure high make-up players progress better. Therefore, I'm pretty confident that low make-up players decline quicker. I've not seen anything that would indicate they "ALMOST inevitably" decline at 27-28. I'd say they take a steeper decline at 32-33 when most players begin declining. But, as I said, I mostly avoid the low make-up guys on draft day and I'm damn sure not going to acquire them in their early-mid 30s so I can't/won't make definitive statements.