I like to think that I know my lore pretty well, but I've been a little confused as to the way soul gems are supposed to work.

So we see in Skyrim that Malyn Varen was able to trap himself inside of Azura's Star, which from what I understand was a failed attempt at him making it into the Black Star. The interior was full of crystalline pillars, which made up everything and he was still in his humanoid form while in the star. So I was wondering if all soul gems have that same interior and if the imprisoned souls are still humanoid and self aware in the same way Malyn was, or if that was just unique to his corrupted Azura's Star.