Audio/Video Call using Wowza gocoder SDK & Streaming service

We are developing a chat application for iPhone & Android and Now we want to add a new feature that is Audio/Video call like WhatsApp. I search for many streaming service provider, In which I like to choose Wowza for streaming services. But I am having some couple of questions:

  1. With the use of Wowza, Can we achieve the same streaming result like WhatsApp audio/video call?
  2. If we try to support group calling than Is there any limit to support multiple active streams?
  3. Which type of stream service should I use to get best results(minimum delay)?