Based on what the users manual says, the difference from narrowest to widest setting on the rear rims with R4 tires is 5.5". I can try and measure the offsets to verify.
I have had the tractor for a couple of months and am at 50 hours now. Almost all of the hours have been moving dirt and grading with the loader and 6' box blade. I am over 6,000' in elevation which takes away some HP. Cab and loaded rear tires, so it is fairly heavy. I really like the tractor and for me I think it has plenty of power so far. I have an old 5' brush hog for my 6 acres, but grass has not needed cut yet, so no feedback on that. I have run the ac on an 80 + degree day, and felt comfortable. The cab gets hot fast in the sun. No noticeable power drop from the ac with what I have been doing.
The tractor is not fast, so if you drive long distance that could be annoying. On flat ground I can hit 16 mph. The two speed shift on the fly HST is very nice and helps on the hills. In high gear, and low HST, it drops down to 6 mph on the hills in my neighborhood.