TL; DR use Jami
You want something to stream low latency, don’t you? Honestly, that means peer to peer, not centralised (I. E streaming to a server which then streams to your friend). OBS will use large buffers (multiple seconds) that are then sent out to the server.
I would suggest using Jami. It’s peer to peer chat with peer to peer video and audio calls. It’s the simplest solution I’ve found. Matrix has MatrixRTC (or whatever they call it) but you will need the Element client and will need to activate RTC in the “labs”. Not sure if it’s in the stable build or the beta.
Signal can also stream peer to peer (webrtc like every other) but it compresses a lot and encrypts on top of it. You could have low latency but you will have visual artefacts and there’s no way to tweak the settings.
I wasn’t aware of WHIP, thank you. Last time researched this there was only LL-HLS which was terrible and when I tried Steam for streaming, it was using RTMP with a 6 second latency.
However, while broadcast box looks nice, it seems to require significant setup to stream.
I don’t know what OS OP is using but on Linux, you can start a video call with Jami (or anything really), then use qpwgraph to send the game audio to the calling application. 2 steps, start call, send game audio to call.
But it’s up to OP what they want to do. It’s been a while, but Jami might support sharing system audio now. Their feature list includes “media sharing” in the call features.