The biggest change that helped when I developed temporary RSI when playing video games in my mid-teens was learning and switching to Colemak.
Natural keyboards (Microsoft-style) helped a bit, but the curved Kinesis Advantage really taught me that you should try to never raise your keyboard angle, and instead keep the keyboard flat at a height where your fingers rest on the home row, wrists straight and naturally held at a comfortable position in line with your lower arms. When done well, it’s like your fingers are hovering over the keys on the keyboard, pushing down, but it can cause strain in your arms as you don’t have any palm rests in this position without buying a Kinesis (and re-learning how to type on a straight column key layout). But by far the biggest difference was learning Colemak, it means my fingers rarely leave the home row and typing is less of a chore on my fingers, but still affects my wrists.
For your mouse hand, the Evoluent mouse may look (and feel) funny, but it certainly is less stress on your mousing wrist. You can fake this with a normal mouse (when you remember to) by rotating your hand, wrist and lower arm 90 degrees, placing your hand pinky side down next to the mouse, palm facing the mouse. Then keeping your wrist in that same vertical orientation, slowly move your thumb and first two fingers to cover the mouse. It’s a loose hold, not as easy to use as the normal grip, but it’s much easier on the mousing wrist. Don’t move the wrist in this position, when moving the mouse, try to remember to move your whole arm if possible. I’ll admit, I only use this mousing technique on days when I’m extra sensitive to RSI, normally my mouse movement is halfway between this extreme and a normal mouse grip—generally I modify the mouse grip to not cup it so tightly with a more horizontal wrist and that works okay...
Also watch out for wrist/finger/positional strain from non-computer activities you do regularly, including how you grip or put extra strain on your body when commuting or when using exercise equipment. There’s always a balance — you want stress to build tolerance, but you don’t want to take it too far and build injury instead. Listen to your body! :)