I agree strongly on trackball being tiring on the thumb. In combination with smartphone use, it's far too much strain on this one joint.
As for straight wrists, I find that naturally happens for me as well, but my impression is that it's not great bc the torsion at the elbow can lead to RSI.
I also don't experience any noticeable torsion at the elbow. Putting my hands in front of my chest is a perfectly relaxed posture for me. Typing is not that different from writing in terms of where my arms and hands are (other than the two-handedness).
That said, I do move around a lot instead of keeping my hands always on keyboard, so maybe that's why I don't experience the typical fatigue at joints associated with keyboard usage.
When standing, I strongly agree with the article that getting some sort of rug is good for comfort. I have a very furry rug for it.
Moving around often is the most important factor, which is easy for me because I like to walk around while thinking.
I find trackballs very tiring on the thumb. Vertical mouse is quite comfortable. Ergonomic keyboard seems unnecessary to me, because I type with straight wrists on a normal keyboard anyway.