As a designer, my right hand is over the mouse a lot of the time. I have a chronic pain on my right wirst, although, I not certain of the cause.
Anyone her has experience with this?
Vertical mouse or trackball; they're all fine, you can get a "nice" one after finding what works first.
Wrist braces.
Wrist stretches.
Exercise; most weightlifting will improve your grip strength which helps some people.
Ergonomic chair; pain in the wrist can sometimes be caused by issues in the shoulder, which often result from a poorly placed arm rest. This is hard to notice as your shoulder might feel fine. Worth double checking.
Reduce stress; some amount of wrist pain can be caused by mental stress which results in tension and blood flow problems.
Laptop; your desktop environment might be great, but maybe you use a laptop too, and you're slowly destroying your wrists on its tiny form factor.
Right now my belief is that non-vertical mice are badly designed and I see no reason to use a non vertical one again.
Years later, I got wrist pain in both hands. Switching to a tenting keyboard solved it. I've used the GoldTouch V2 for 7 years now.
Do not try 3M's vertical mouse with the thumb button. I used it for a few months and developed severe pain in my thumb. Fifteen years have passed and my thumb still occasionally clicks when I bend it, due to that injury.
I think you will notice a loss of precision though. For example I could never play an FPS at my best with a vertical mouse. But for $80-100 definitely worth a try for your health.
The thing that's hard to remember with a vertical mouse (and mice in general) is that you're supposed to move your arm, not your wrist. Getting used to that was more of an issue than the orientation of the mouse.
In the end my favorite is the Logitech Ergo with the "Plus" stand. The version that includes the stand is only sold in the US so I imported 2 of them. I got rid of all the others.