Be careful with such a small keyboard. Taking notes in multi hour lectures with an Apple Newton keyboard gave me permanent RSI 20 years ago that I still have today.
When using the Mini 9, my wrists are not on the palmrest: the keyboard is so small that my palms extend above its edge. So, the wrists are not relying on anything, I keep them "in the air" while typing. This appears to give the wrists constant movement and flexibility, thus resulting in less tension.
I suppose this wrist position must be closer to "correct ergonomics" as shown on e.g. this photo: https://www.daskeyboard.com/blog/wp-content/uploads/2011/11/...
The Mini is 8.9". Interestingly, with any bigger machine (even a 10" netbook), I cannot constantly keep palms "in the air" the same way. When the palmrest is bigger, I'm leaning on it, and can't help it.
I emphasize that this is anecdotal, though. I'm an end user; do not make ergonomics decisions based on what I say. It just seems to work for my body.