If I wanted to build a Twitch clone for internal social activities at my company, would this be a good tech stack for that or is WebRTC not the right fit?
You certainly could, there are some folks in the community building Twitch-like livestreaming experiences with LiveKit. One of my teammates built a mobile livestreaming demo app, perhaps I can convince him to release the code. ;)
Update:
Given that this is for internal use at your company, a single LiveKit node should be perfectly fit to handle the scale you need.
You can definitely use Daily to build a Twitch clone and beyond — we have a powerful API for custom layouts and graphics in live streams.