The cause of my RSI was using arm rests on the chair and resting the wrists on the desk. It led to scrunching up my shoulders which ended up causing severe neck and shoulder soreness. This setup also caused pain in the underside of my forearm when using the mouse for extended periods of time.
So I got rid off arm rests on my chair and put the keyboard and mouse on a tray and put the tray on my lap. That was the neutral resting position for my arms. And it got rid of my RSI for the most part.
If you've tried other options for your RSI and still can't find respite, check if typing from your lap alleviates pain. You can test this using a laptop. If using your laptop on your lap for long periods feels less stressful as opposed to typing and mousing from your desk, it means the least stressful position for your arms is at the level of your lap.
So I got rid off arm rests on my chair and put the keyboard and mouse on a tray and put the tray on my lap. That was the neutral resting position for my arms. And it got rid of my RSI for the most part.
If you've tried other options for your RSI and still can't find respite, check if typing from your lap alleviates pain. You can test this using a laptop. If using your laptop on your lap for long periods feels less stressful as opposed to typing and mousing from your desk, it means the least stressful position for your arms is at the level of your lap.