You could develop an extension entirely without the rig.
You could build something that uses no Twitch Features and thus no need to touch anything from the Twitch JS extension helper, which is what the Rig simulates.
So, we should start at the beginning.
A Twitch Extension is, basically, an iFrame.
That iFrame loads a website consisting of HTML, JS and CSS, (and perhaps some other things)
So, if you can build a website, then you can build a Twitch Extension.
Anything else on top of that is to do with Twitch Interactivity, as provided by the helper. Or something EBS/backend servery, which isn’t simulated in the rig anyway.
So the question is, rather than pointing you to a video about the rig, what are you stuck with?