When it comes to load testing, WebRTC is different. And that's because WebRTC is peer-to-peer and not client server.
What you can test is the client server part, more specifically the signaling server and the STUN/TURN server. For these, you can easily use JMeter as for any web server. For STUN/TURN just follow the specs (though if you're using an existing server, I would leave this into the authors hands, unless you want to involve in that project too). For the signaling server, it depends on how you build it.
What you can also do with WebRTC is try to test with a controlled limited bandwidth and delay/jitter. This will be more like a smoke test, than a load one. To do this automatically is a little bit more complicated. especially if you want to do it with audio/video, not data.
