This was the idealized, middle-class version of reality. You would see a lot of extramarital sex in the upper and lower classes, while a lot of premarital sex was happening in working classes too. Usually the version of society you hear about represents only a small minority of the population at the time, usually middle-upper classes. However, I can’t speak to the alcohol consumption. Will edit with sources momentarily!

Edit: Unfortunately I’m not tech savvy enough to link pdf papers (was posted on Moodle so I think it’s not general access available) but an article called “Dance Madness” by Kathy Peiss illustrates the youth culture of the early 20th century- not at all the chaste, moral image portrayed today.

Anna Clark also has a really good book on historical sexuality. It’s called “Desire”. Definitely worth a read!