There is an issue with how Miracast behaves on Surface Hub that could cause iOS/Android devices to perform very poorly when mirroring to AirServer for Surface Hub. To prevent this lag from happening, you will need to change the Miracast channel to be set to 11. This can be done as follows:

  1.  Open up the Settings app and go to Surface Hub and then Wireless Projection. 
  2. Change the Miracast channel to 11. 
  3. Make sure to restart the Surface Hub.