So is it then possible to edit npc stats for example Mjoll the Lioness is horrible at sneak she keeps getting caught! If I use setav sneak 100 on her she should have a sneak level of 100?
Select the NPC and use getav xxxx (health, sneak, stamina, etc) you can also mod their stats accordingly.
You can also give them spells and whatnot, but it's tossup whether or not they'll properly use them, since it's usually up to the scripting. But, I suppose if they have the skill, they'll use the spells/abilities.