I haven't tried the particular keyboard you referenced. But I went through a phase of building and testing such keyboards - mostly variants on Doug Engelbart's

I haven't tried the particular keyboard you referenced. But I went through a phase of building and testing such keyboards - mostly variants on Doug Engelbart's design. I could never get decent speed and some chords were harder on my fingers than a regular keyboard. The biggest problem is that with five fingers, the maximum number of chords is 31 before you have "slide" positions, i.e two or more keys to one finger / thumb. Remembering codes for characters took a lot of time too. Might be far easier to investigate exactly how and when the nerve pain arises. I used to have a massive issue with mice. Solved it by using a trackball under right hand and a mouse (with optical sensor for positioning disabled) under the left hand. So I wasn't moving the mouse and clicking at the same time. That was enough to overcome my RSI issue. I also currently use a MS Curve keyboard. It is what works best for me. Some of my colleagues use those weird MS ergonomic keyboards with split areas and funny looking wrist rests.