Personally, I would regard AK as about a half-day park, even if I have "days to burn" at WDW, and MGM as no more than a 3/4-day park unless I have "days to burn." Indeed, if I'd known that the old Animation Backstage Tour had gone bye-bye along with the on-site working animation studio, and had been replaced with something approximating the Animation building at DCA (including the same "Drawn to Animation" show I can see at DCA), I quite literally wouldn't have done anything at MGM other than riding GMR (twice, once each scenario) this past November (when I was a bit short on time), reducing it to less than a half-day park.
Epcot, on the other hand, is at the very least a day-and-a-half park, and that's if you only hit the highlights (like Mission:Space, Test Track, American Adventure, Maelstrom, Ellen, SpaceShip Earth, and Imagination). And MK is at least a full day.
I've only had direct experience with the now-discontinued "Ultimate ParkHopper" length-of-stay ticketing, in which hopping privileges are a given, but I think I'd still opt for the hopping privilege under the new system, just for the flexibility: there could easily be several things happening on the same day in different parks, and not any other days during my stay, or I might have dinner reservations in one park, but a special event in another. I'd much rather stick with a rather Spartan hotel (e.g., my old standby, the All Star Music) and the hopping privilege, than a more expensive hotel without it.
I don't know, however, if I'd spring for "plus": it wouldn't be cost-effective for just a single trip to PI, and I don't have any interest in visiting a water park. So I'd also have to plan on trying DQ, at the very least.
As far as structure goes, I tend to be sort of middle-of-the-road: I don't plan out some detailed, optimized itinerary, but neither do I just go out without some sort of plan for the day. I'll typically know when Spectro is scheduled to run, and book the BackStage Magic and Steam Trains tours, as well as a side-trip to Kennedy Space Center, and I'll typically at least try to book dinner reservations for Cinderella's and the Liberty Tree (but if you're willing to dine at odd times, they may be able to work you in without a reservation; just don't even think about doing the Princess Breakfast at Cinderella's without a reservation!), but other than that, I just try and do whatever catches my interest.
Incidentally, if you want to avoid wasting time, make sure you have a guidemap for AK. You can find your way around MK, Epcot, and even MGM without one, but at AK, well, I spent over an hour wandring around trying to find Dinosaur last Fall, having ridden it twice before, and finally ran out of time.