Thanks for the heads up! We've taken a look and so far seems like we add value in different ways since they focus on mobile engagement, but definitely will consider this going forward
Thanks for asking about this. We don't expose our APIs at the moment - because the SDK is how we achieve extremely high performance / reliability. The SDKs do a lot of optimizations for you because a standard API round trip can be pretty slow.
2. Actually fairly granular, especially if you have properties or attributes you want to filter populations on.