"what's your angle" is often used to mean "how do you profit from this". In other words, what aspect of this benefits you, or how do you make this benefit you? The emphasis sometimes being on what you have to do to make it pay? I see that you have an interest in the expansion of this shopping area, but what's your angle? That is, what aspect do you get benefit from and how? Often used for non-obvious things, such as business or scams.

Yes, it means what’s your purpose? Or what’s your opinion? You could also ask: What’s your deal? What’s your angle here at.....? What’s your take on.....? What’s your opinion on....?