I think we can. If I were an Elder, I would choose humani that suit my personality more. Less misunderstandings that way. But because we are talking of beings that are fro another race and time, the different beings will act differently, but that doesn't mean similarities can'texist. My point is that finding similarities between the Elder and the humani would be helpful, but you can't totaly rely on it.
As for Machiavelli, I think that he will try something that will risk his immortality, but with hope that his Elder doesn't find out. Something like give information to the Flamel and the twins about who to trust, what to do, without his Elder finding out. And then, if Flamel gets the Codex back, he will ask for the Philosopher's stone from Flamel and turn to he good side, when his immortality isn't at risk.