Actually, I generally don't pop the p in "yep" and "nope." When I describe someone popping the final p in a word, I mean a loud, intentional pop that almost makes the p its own syllable, like overenunciating the final t or d. It's a kind of verbal punch--almost phonetic punctuation--as opposed to the normal plosive we use in regular conversation. (It's usually Gabriel I show speaking that way, if that helps.)
ETA: Here's an example, though the popped ps in this case are initial:

[/pedantic pickiness]


Anyroad. Hey, you! *waves*