To be fair, underwears are quite recent invention in human history.
Therefore, it would be appropriate or immersive that nobody wears any underwear in MEDIEVAL fantasy setting.
Yes this is why, good sir, BG3 characters should be naked beneath their cloths.
Medieval people were totally wearing underwear, but not the kind that we wear nowadays. I get your point thought, the underwear in BG3 is a couple centuries too modern.
Chemises, under-bodices and braies aren't as sexy though, lets be honest.
