Video-conferencing on two raspberry pi 3


I’m coding a video-conferencing prototype with bi-directional video streams on 2 rpi3.
What is the better option and is it possible to be in peer-to-peer mode?
Shall I use gstreamer, ndi, webrtc, rtsp or ?
For the prototype it consist of playback of 2 videos on a LAN, then I have to test with a ip camera/webcam feed, then on a WAN…
Thank you for any hint!