I'm going to address each of your points in turn:
This is a really cool idea! I'll catch it on youtube as it seemed when I tried going on the stream as if all audio is muted. I'll wait for a youtube video, and/or try to watch next time.
There is only a small stretch where the audio is muted (the timeline is red) and I was just bullshitting around. Twitch, a lot of times, defaults for me to having the video proper muted. Try again.
It'd be really epic to learn some scripting stuff & other advanced thing possibly. Scripting in particular seems really hard to "break in" and really get the logic of how it works.
Doing a proper tutorial with scripts will be tough, especially given the live nature of Twitch streams. What I can do is pick a few scripted things, pre-implement them, and then go over both what I did to set up the records in the CK as well as go through what the script does line-by-line.
I'm kind of hung up on the idea of if I make a Commercial Plot it should sell stuff I made, and that if I make anything I want it to be implemented in game via a Commercial Plot as IMO that's like the most lore friendly way.
Well you're in luck then. In the Sim Settlements series of tutorials I'm going to make 1 of each building type, working my way up in complexity (-ish).
IMHO, the complexity for plots go
1. Recreational & Martial.
2. Residential & Agricultural.
3. Commercial.
4. Industrial.
5. Advanced Industrial.
We are starting with Residential (which we should be able to finish on Wednesday) just because, and on Friday we should be doing Agricultural (which will take 1-2 sessions). I'll then go to recreational where I'll focus on retexturing stuff (1-2 sessions), so that one has an added bonus. We'll do Martial after that and I'll try to show how you can use the plot to spawn NPCs (another added bonus) (1-2 sessions). We'll do Commercial after that and this will probably take 3 sessions. I'm going to set up a custom vendor with y'all and do some basic kit-bashing to make a custom item that the vendor can sell (lots of added bonuses) and a custom piece of furniture. After that we'll do Industrial and we will set it up to produce custom items (borrowing from what we learned before). Then to cap off the plot-type tutorials we will do Advanced Industrial which may take quite a few sessions (I have no way to gauge this).
Once those are done, and this looks like over a month of streaming!, I will probably do a couple "script tutorials" where we go through the logic of some existing scripts, and if I get enough easy ideas I may implement something new.
I plan on the Sim Settlements tutorials to cap with implementing a custom leader (we may do a 100% custom NPC) and custom flag (texture work!).