I found that switching to a mechanical keyboard was not only a joy because of the clickyness but also a noticeable improvement in how long I can type without strain. Now I'm too fond of it to ever switch it out for a wavy keyboard. A while ago I tried to add a Wacom tablet as a mouse replacement, as it has worked wonders for some people after you get used to the display locations being mirrored on the tablet. However, I get more RSI from thin pens / styluses than anything else because I use too much force to hold pens. Good thing I kept the receipt on that one.
Never tried an ergonomic + mechanical keyboard so your mileage may vary. I will say that I feel the same thing on styluses pressing on hard screens, made ~10x worse with fingers on hard screens, fingers on touchpads, and fingers on low depth keyboards (a la mac keyboards). Something about the backpressure just makes the tendons inflamed lightning fast. Vertical mice did wonders for me though. Let me know if you find a better solution, keyboards and mice are mostly a solved problem for me, but hard glass screens and stiff buttons are still my Achilles heel so to speak.
Does your phone have haptic feedback? As in, it vibrates a bit when you type/press things. The main reason most people press too hard is because they want to make sure their press registers. With haptic feedback enabled it's easier to teach yourself to tap lighter on smartphones/tablets.