While this page lies under the Emacs section, I don't have strong opinion on whether Emacs users have disproportionately high RSI or similar issues.
This page is meant to document the state of my RSI and what I have tried or am trying. I guess a lot of programmers go through this so it might be helpful to put more experiences out in the open. Saying that, don't follow any random advice on the internet (including anything on this page which might look like an advice). RSI is not very well explained medically and you will have to maneuver your way through a bunch of experiments yourself.
I started developing RSI symptoms around 2017. I was using my laptop keyboard (HP Pavilion dv7-7012tx) and noticed pain in left arm starting from fingers. My posture was convincingly bad. I would lie down with my back up and program for long sessions. A few months in, I switched to Microsoft 4000 and set CTRL on CapsLk1. That helped for a while but my posture still stayed relatively stupid.
Then in early 2019 I got another bout of pain. This kept on for a couple of weeks and I was diagnosed with RSI. Told to take breaks. Later in the same year I got another hit. After another RSI diagnosis, I realized that using 4000 specifically was hurting since I had to press harder than I can on my laptop keyboard (Lenovo Legion Y720 since mid 2018). Another important thing I noticed was that the length of the keyboarding session mattered a lot. If I try to stretch it beyond a point, I will start feeling that something is going to go bad. I also started using a wrist splint for left hand through those 2-3 weeks which helped tremendously.
At the moment, if I know it's a long programming session, I tend to use org-pomodoro to remind me to pause every 30 mins or so. Also I continue using the splint even after the pain is long gone. While it's not needed, it does help in setting my left hand straighter. Plus I maintain a better posture now, usually a seated-on-a-chair one and not something to do with a bed.
This helped with unusual pinky contortion since I am on default Emacs bindings.