I just bought a 2011 KP, went for 600 mile ride last weekend. First Vic i have owned. Handles great, put a set of X-BOW pipes on. Hate the stock seat, my wife says the rear seat felt like riding a 2 x 6. Have looked at the Vic touring seat with back rest and may be a Mustang. No experience with either. Looked at Vic bags but all seem too small.
If anyone can help me with the seat and bag issue that would be great.
You've asked some excellent questions and there are some varied answers to them.
First of all, I had a Jackpot and not a KP, but they have the same basic suspension and somewhat the same handling characteristics.
The good news is Mustang does make a touring seat for your bike. The bad news is your bike will never be a touring bike. I might get slammed for saying this but the KP, Vegas, JP, and Hammer are all day cruisers and not meant to be long haul bikes.
Having said that, many have transformed the KP's and others of the Vegas-class bikes into pretty good medium range tourers with good seats, like the Mustang and Corbin, and even the Victory offering. I've read many people actually prefer the Victory seat over the Corbin or Mustang.
(A guy who's nickname is Rollin put 200k miles on a KP and lots of very long distance Iron Butt rides on his KP that's now in the Victory Hall of Fame (if I'm not mistaken))
Another option is to get whichever seat you like best and have someone, an upholsterer, tweak it to your satisfaction.
The biggest difference anyone will find between the Vegas-class Cruisers and the Vic Tourer's (Vision, XC/XR) is the suspension and then only on the back end. The Vegas-class bikes have 3" of travel whereas the Tourer's have almost 5". May not sound like much but it is when it counts and the tourer's have air shocks that can easily be pumped up or down depending on the need.
Ok, that's all I got for now, but if you have any more questions; there are lots of great people on this forum to help out.