Agora's SDK 3.0.0 allows users to join an unlimited number of channels, with a limitation that only one camera feed can be published at a time. This feature could be useful in situations like classrooms where the teacher streams to a main channel and students perform group work while still being monitored. The setup involves creating an iOS project in Xcode, installing CocoaPod AgoraUIKit_iOS, setting up UI views for audience and broadcaster roles, connecting to both channels, displaying video feeds, and leaving the channels when necessary.