Why does WebRTC use UDP?

NAT Traversal requires UDP. Without NAT Traversal establishing a P2P connection wouldn’t be possible. UDP doesn’t provide “guaranteed delivery” like TCP, so WebRTC provides it at the user level.

See Connecting for more info.

How many DataChannels can I have?
65534 channels as stream identifier has 16 bits. You can close and open a new one at any time.
Does WebRTC impose bandwidth limits?
Both DataChannels and RTP use congestion control. This means that WebRTC actively measures your bandwidth and attempts to use the optimal amount. It is a balance between sending as much as possible, without overwhelming the connection.
Can I send binary data?
Yes, you can send both text and binary data via DataChannels.
What latency can I expect with WebRTC?

For un-tuned media, you can expect sub-500 milliseconds. If you are willing to tune or sacrifice quality for latency, developers have gotten sub-100ms latency.

DataChannels support “Partial-reliability” option which can reduce latency caused by data retransmissions over a lossy connection. If configured properly, it has been shown to beat TCP TLS connections.

Why would I want unordered delivery for DataChannels?
When newer information obsoletes the old such as positional information of an object, or each message is independent from the others and need to avoid head-of-line blocking delay.
Can I send audio or video over a DataChannel?
Yes, you can send any data over a DataChannel. In the browser case, it will be your responsibility to decode the data and pass it to a media player for rendering, while all of that is done automatically if you use media channels.