Mechanical Keyboards are nice obviously for the tactile difference and impact on typing speed and sensitivity, but for me the game changer was switching to a split keyboard for the ergonomics. I have always had shoulder pain, and tightness in my triceps. No matter how much I worked on ergonomics .. mouse position, height, etc. I have very broad shoulders/chest, so putting my hands on the keyboard always bowed my chest in and rotated both shoulders slightly forward.
I use the UltimateHackingKeyboard (UHK) now for over a year, and my shoulder and arm pain have all but disappeared. The UHK comes with a relatively short 3-4 inch cable to connect the two halves, and I found that was even to close together. I've since replace with a 12 inch cable and each half of the keyboard sits directly in front of the corresponding shoulder. This lets my arms, pecs,triceps, and back muscles all be in a relaxed position.