Looks like you have made up your mind against pressurization. Which is a good thing. It's not only the turbulence that you will fly into because the little radar didn't quite show you the right colors. But at FL200 and above you will encounter severe icing, which is going to bring you down anyway. Those levels are the worst to fly in, even in turboprops such as B190. You want to stay below or way above that icing zone.
Regarding the Piper twins: I have sent you a contact, he does operate a Navajo and knows about the strong and weak points of Navajo and Chieftain. Bush operations is possible, same as Cessna twins. Range is less than in a Cessna and so is cabin space. We did a few ambulance flights in a Cheyenne, very much a pressurized turbine Navajo. It is rather cramped and one has to wrestle the aircraft all the way. It's easier to push an angry Brahman Bull by it's horns backwards into a horse trailer. The Cessna 400 twins are much nicer aircraft to fly.