Lightcycle, I used to get sore wrists and hands, similar to the start of carpal tunnel, and still do at times. I have large hands, and gripping the handles feels like gripping a pencil sometimes. That was the cause for me. I stretched a silicone grip over the existing one, and that helped quite a bit, although it still feels a little small. Maybe that'll help you a little?
FYI, I know what carpal feels like because I've had a mild, recurring case back when I worked at Blue BIrd in the 90s and early 2000s as a riveter. Not fun since it effect everything you do with your hands. Mine was only in the right hand, which happens to be the throttle hand.
My but gets sore on long rides, but that's minor. If it becomes a problem, I have a gel pad I can slip under the seat upholstery.
My back, despite two herniated disks also acquired at Blue Bird, from which I have recovered to about 97%, should never be a problem because of my bike choice. Most people seem to hate the Katana, but that is the perfect bike for me because it allows me to sit in a variety of positions where I can either learn on the bars, taking weight off my back when needed, I can sit straight, or I can hunch back. It has to do with my long reach combined with the seat height, the handlebar height, and the distance between them. It also has a high seat which is well suited for my long legs.