I just found out that the words yup and yep have a slightly different meaning. Here’s what I’ve learned today.
They have the same meaning, but there exist slightly different inflections and connotations.
“Yep” is active; it is a go-getter; it implies that you are excited to respond in the affirmative, and is more playful than using “yes” but less committal than “definitely” or “absolutely”.
“Yup”, on the other hand, is slow, perhaps drawling. It is likely a response to an informational query and shows that you may not be totally pleased with having to answer. In some cases, it may contain sarcasm in response to an obvious question or overly inquisitive interrogator.
Thank you Kristján!