It’s actually the short cropped under blouse that determines the Dirndl’s level of modesty. My daughter bought one for herself two years ago, and has switched out the blouses for different styles.
What I’ve always found both fascinating and lovely is seeing young people in their teens and 20’s still willing to go out in public and party wearing Tracht aka.. Dirndl and Lederhosen.
Although Oktoberfest or die Wiesn begins at the end of September, the festivities of Bierzelt begin in upper Bavaria during the summer, usually in late July, and you will still only see a small minority who won’t wear Tracht.
Yes, the under blouse I had with mine was not low cut and it also did not have puffy sleeves. It had regular short sleeves with a thin row of lace around the openings. The same lace was around the neck line.
That is interesting that young people still enjoy wearing the traditional garb.