One computer will handle all streams and (re)stream a mix of all 4 streams (in a 2x2 grid) to twitch
Internal latencies (local network) are about 25ms. I’m expecting that to go higher over the internet, but I already tested from my job to my home and the latency was around 200ms, not bad.
The problem with restreaming from other’s people live streams is that twitch/youtube by themselves have like a 10 second (that’s 10,000 ms) delay. With NDI even if the latency is 1 second, is still much better and can be appreciated. I’m not expecting perfect sync, but something that can work.
Of course you can always use render delays in OBS to perfectly sync all streams, but that’s a lot of (IMO) unnecessary work.
Audio wise, I’m going to feed just one audio feed (mine) that will include both Discord and the game (all other players games will be muted to avoid an audio mess).
I don’t experience the discord delay issues you talk about, might want to check your audio/network settings on both Windows and Discord, something must be misconfigured on your end.
I also don’t monitor the stream audio, as to not hear myself with latency. As long as the audio bars are moving, everything should be fine
Lastly, I have a dedicated PC for streaming, so my computer running the game will work just the same as the rest of the players, only difference is that mine is expected to have lower latency due to it being on the same network of the streaming PC
