I have been a practicing historical reenactor specializing in portraying a German Landsknecht circa 1520. I have lived in slash and puff clothing 24/7 for up to weeks at a time, sitting, walking, eating, cooking, marching and fighting (full speed/full contact martial arts). I have done this for more than two decades now.

In addition I have done extensive research on the garb of all european countries from the period beginning 1475(ish) through 1550. The definitive resource for German garb is "The German Single-Leaf Woodcut, 1500-1550" which is part of a 4 volume set. This book has the most comprehensive collection of woodcuts showing everyday life in Germany; Landsknechts are featured heavily.

The slash and puff garb was pervasive throughout all ranks of the Landsknecht army. With the additional influence of slash and puff garb being worn by the Swiss mercenaries, slash and puff began to be incorporated in many western and central cultures garb by the mid 16th century.

As for comfort, slash and puff is very comfortable. It's a combination of tight and loose. Most of my garb is combinations (layers) of wool and linen which can either cool or warm as needed. You move easily and don't feel bound up. In every day life, I am especially careful when around doors, as door handles will reach out and grab me every time. Other than that, such as times during combat, when something fouls on my slash and puff it's usually violent enough to simply rip through.

Feel free to ask for me to clarify more if you have specific questions.

Followup for clarification: I forget the word for the style but did it not originate with cutting looted clothes so they would fit? If so, doesn't that explain that it was in fact a practical method of wearing clothing that didn't fit?