Um, well. I'll start with Paul since I'm signed in here. I think mortal!Paul doesn't have the confidence Poseidon does (yet, at least) and he's much more level-headed. However, the temper is extremely bad for the both of them. It's just that Paul burns a lot slower and is more passive about things, whereas Poseidon is an angry piss-ant all of the time. Overall, I think he'll evolve more into canon Poseidon's personality as the transformations go on and as he develops the weather-control ability.
For Gabby, well. Glinda is true to canon exactly, I would like to think - even though she only got to come out once - but Gabby is a good person too, she's just not as pious as Glinda. That will probably bother her but it's not like anyone can be as good as Glinda. :p She'll just have to learn to deal with it, as well as Glinda's penchant for lesbianism. Come on! She had an all-female army!
Shere Khan is actually a combination of the book and multiple movie personalities - he can be a bully and rather pompous like in the book. Although it's ironic that Disney gave Shere Khan more of a villainous role than freaking Rudyard Kipling. I actually like Disney's/every other movies portrayal of him, as something sophisticated and deadly, but as some versions have suggested, he is merely distrustful of humans because of their treatment toward animals. It's hard to look at him as a 'villain' in that light. Naturally, the tiger's opinions really conflict with Sam, but they have a few things in common. Tigers are determined, and they have very powerful and dominating personalities. I think there are lots of similarities there. Even if Sam would disagree with me.