Is react-native-webrtc use H.264 as default?

I am using react-native-webrtc to stream camera feed to Wowza. Is react-native-webrtc use H.264 as default for iOS and Android? How can I know if I am using H.264 or VP8?

No. It uses VP8 by default. You can change this by munging the SDP and putting H.264 first, if present.