I've been battling wrist pain from typing for the past year. I've used just about every commonly recommended ergonomic keyboard that's ever recommended on the internet, in addition to a variety of mechanical keyboards. The ergonomic ones either temporarily alleviated pain and then it returned, OR the pain got even worse. I currently use a Filco Majestouch 2 TKL with MX Brown switches and it seems to be okay for the most part but get occasional wrist pain.
I do hand/forearm/shoulder/neck stretches daily. Again, they temporarily make me feel better but some days I get sharp wrist pain and my forearms feel like they're on fire. Given that I get pain for almost every keyboard, I'm guessing the problem has more to do with my posture and desk ergonomics. I'm not sure what to do at this point besides seeing a doctor or chiro.
Also, consider that it may be pycho-somatic. No, that doesn't mean you are crazy or the pain is not real it just means your subc mind has zeroed in on your wrists to express conflict (my take). The best book in this area is by John Sarno, Healing Back Pain: The Mind-Body Connection. You can ignore his Freudian rage theory (he wasn't a psychologist) but learn his techniques and you may have success as many people have using his advice, myself included. I completely cured my "RSI" in about a month and can type for hours now without problems.