RSI is a combination of "repetitive" and "strain". My take on it is that ergonomic keyboards that limit the amount of finger movement make your typing more repetitive - hence you need to be sure as hell that there is as little strain as possible.

I also went with a minimal split keyboard and quickly started to feel pain. When I however looked at my desk/chair/screen, I found that they don't promote the correct posture. Once these were corrected, I got no pain at all.

I think the right lesson is that this is a journey, rather than a problem you can throw some money at once and have it solved.