I think POW should be flannel or tweed. I haven't seen an example that looks good as a worsted. For worsted, I think nailhead, sharkskin and Birdseye are better alternatives.
I have a DB in the LL RAF blue POW Piuma. It's ok but not great.
I think is really interesting that Boyer's connects Cary Grant and Castiglione's idea of sprezzutura. According to this post on sprezzuturahttp://tuttofattoamano.blogspot.com/2015/06/sprezzatura-great-philological-debate.htmlAccording to Boyer, that is exactly what Grant did, he made himself better through training.
My current tux shirt has 3 buttons so there are some vintage studs to choose from. I wear a vest with mine so I think a 2 button tux shirt will work too. My understanding is that there are more vintage options for 2 buttons.
I recently got vintage abalone shell stud and link set from the 1940s. I think the next tux shirt I'll get will have 2 buttons because Manny (from the Missing Link) said that the studs he has from the 20s are often 2 button. I think the vintage buttons are often so much more beautiful than the ones made today.