Just out of curisosity ...
Wich century you think is in BG-3, compared to our world? And more specificly ... based on what?
Much of the sword coast presents itself as a euro-centric late medieval fantasy setting. There are many other styles involved in the wider world of Toril (Rashemen and Icewind Dale are very heavily Conan inspired), but it should be mentioned that the styles of fantasy involved in the creation of DnD as a whole come from many varied sources set in many different assumed time periods, and as such the stylistic aesthetics of Toril change dramatically depending on where you are. Same is true for the fashion. And all of it is completely irrelevant because I don't actually want a true to middle ages mudcore aesthetic in my high fantasy video game, so having modern underwear isn't really a problem.
