Well okay I'll try
A pen & paper RPG is much more like a adventure where you must find clues and talk to people to advance in your quest. So a computer adventure is like an RPG with no stats and fights.
A computer RPG is based on the fighting system of a pen & paper RPG. You have the stats, hitpoints and skills/spells. I would say 'tradional' computer RPG's (AD&D, Ultima, Might & Magic) are closer to strategy games than P&P RPG.
That's why I would say Elvira and Waxworks are RPG's (you have to solve puzzles and fight enemies), but you can count them as Action-Adventures which is also true.
These games are hybrids and somehow unique, so it's hard to put them in one corner