I've had a similar experience streaming on FIOS. I do not have a dedicated system, it's sharing its time with Homebridge, Frigate, Channels DVR, and a bunch of other small things. CPU hovers around 50% when streaming and recording with a lot of stutter.
It seems like watching live is better than recording and streaming, so I was thinking of trying to get a dedicated system. Might not make a big difference.

. If you manage to get anywhere, let me know! Still would be great, and, if someone can get it to work reliably for NBC, Iād probably use that instead of my Mac solution!