this is a great writeup, been looking into owncast myself for a while. the caddy + multiple instances setup is clever, didnt think about running separate owncast instances on different ingest ports like that.
for Frisk - from what bcoyle showed, 1080p/60fps gaming at 6800kbps should work fine on a pi 5 with 1-3 viewers, especially if you use x264 encoding on the OBS side and set owncast to passthru mode. that way the pi basically just relays the stream without re-encoding and keeps cpu usage way lower. just make sure you dont run multiple instances alongside it.
one thing worth mentioning for anyone who finds this thread and just wants owncast running quickly without messing with the install - theres a project called Syncloud that has owncast as a one-click app for raspberry pi. handles the ssl and reverse proxy stuff automatically. i built it so im biased obviously, but it couldve saved some of the initial setup headaches. that said the manual docker + caddy route gives you way more control over multi-instance setups like bcoyle is doing, so it depends what you're after.