2) Adding key frames increases the bitrate greatly which exacerbates problem 1.
2.) I am not aware of a way you can no keyframes, but be decodable at anytime. I just have done it 'HLS Style' or WebRTC 1:1. Curious if anyone else has different solutions.
2) Yes, you either need a high keyframe interval or some type of out-of-band signaling framework to generate keyframes. WebRTC uses RTCP. A good question is why does WebRTC feel RTCP is necessary at all? Why not generate a keyframe every N seconds like you do with HLS and remove the complexity of RTCP entirely? The answer is that many clients cannot handle the bitrate at real-time speeds.
Only naive implementations would burst an IFrame on to the network, most pace them. And if needed, you could split your iframe into several frame intervals and decode them without creating a burst by bit rate.
Actually a lot of webrtc implementations use 1s or 2s GOP length. Again depends on how much control you’ve on your pipeline. Browsers implementations do make some assumptions on usecase.
2.) I use the same tactic as HLS. Generate your video with a reasonable (~2 seconds) keyframe interval. When a new client connects start sending at the keyframe.