This isn't really a game for playing "stealthy" characters, although there are stealing mechanics in place.
While there is a sneaking system it is mostly based on noise, not visibility, and is really only useful for robbing houses. Pickpocketing is a dexterity-based skill check (the more paranoid the person is the higher your dex must be to pickpocket them without detection) and is a great way to earn lots of gold and experience; all named characters have something that can be pickpocketed (with very few exceptions). There is no backstabbing whatosever.