Yes the small Mules have selectable locking rear diff, and no engine braking. And the brakes on mine took a lot of effort slowing down when loaded on steep hills, but that was a 2006, Kawasaki may have improved them. The Mule Pro MX has the locker and excellent engine braking though.
I can say not having a differential does chew up my trails on the turns. I had the same issue in a few places with the Ranger mostly at sharp up hill turns because though it had a differential it HAD to be locked before it could go into 4WD which is crazy! I try not to take the P520 on my trails that have tight corners when it's wet. A neighbor has a P700 that he often has to drive up beside his garage then turn across the driveway and that little area is almost bare of grass. And his rear tires wore out after 3 years which isn't surprising as he rides it on pavement some. But he loves the fact that it "goes almost anywhere in 2WD".