As far as the APP goes, it will help you in requesting a sight, but there is no guarantee you will get what you want. If you are willing to move in a day or two, you can sometimes get your fav spot after someone checks out. I have done this a couple of times. It is a pain, but I think worth it.
We have stayed in different spots that were "just fine", but once had a spot that was a real PITA to back into. I am a Mom with 4 sons in a 2011 F350 SuperDuty, pulling a 2011 34'6" FW. It was about 5 or 6pm (after driving 2 days) when we pulled in, and the loop was pretty full. I must mention we were there for
MNSSHP and the F&W Fest.
The loop where they put us was next to impossible for me to back my rig into, and I do not usually have problems backing - I am a 2 shot wonder! It was an inside site in the 1300 loop and that is probably fine for any unit less than about 28', but the way it curves there is no easy way for a large rig to back into an interior spot when there are vehicles parked all the way to the road on both sides. It is a pretty good 100 angle backing.
Unfortunately we had a problem with our FW and had to take it in for service so I inquired if I could move to my FAV spot and luckily it was just vacated so we moved. BTW, I will just say my favorite loops are the 400 and 500 because they are so close to the boat dock. We came home late every night MK was having EMH.
But like all these folks are saying it all depends on what you are pulling and what your wants and needs are. We never took the DW buses to the other park, we drove the truck for flexibility, so being near the dock was great for us. We also never use the pool or bath facilities, so again they are moot points for us.
Good luck with you trip, hope you get "just the right spot" that works for you.