The iOS 9.3.3 beta 2 seems to be a firmware filled with various bug fixes and under-the-hood changes. It is important to note that there is now also a iOS 9.3.3 beta firmware for the 9.7-inch iPad Pro, which previously bricked tablets for some users.
iOS 9.3.3 beta 2 can now be downloaded by developers via Over-The-Air update, or through Apple's Developer Portal. We'll be sure to hear more about this and the upcoming iOS 10 at the Worldwide Developers Conference on June 13.