I did. I was making a Twitch bot. It was fun, though managing my secrets (such as Twitch authorization tokens) was PITA.

I do it all the time. Hard to keep viewers around because not everyone enjoys programming (especially watching it). I worked on Discord bots, websites, Twitch bots, etc. I enjoy to code, so it being fun is just from me enjoying doing what I like to do. Do not be discouraged if you pull 0 viewers. Do it for the fun and if you do get people, try to engage with them and explain some things.

I mostly work with JS and Node while on stream, so I just store my tokens and stuff in a config.json file that I never open on stream. I can easily call these files and get the information needed.

Go for it! Throw out projects all the time? No worries. If you say you're a coding stream that's only how people find you. Viewers stay for the personality. Explain what you're doing and try and engage the audience while you're at it, and it won't matter what you're actually doing.

I have never done it. I stream Minecraft on twitch as a way to chill. I do development alone, and I find myself being much more productive when there is no external input from anybody for a long period of time.

I suspect it will be very fun thought to do something like with my YouTube subscribers, since I have a youtube channel about web development. But I never tried because of different time zones me and my fans live in.

I do it sometimes. Some people visited me during my streams, but like Jacob said it's hard to keep them around :) I use twitch to add some motivation on me so you should do a project that is important to you, among the projects you throwed out :)
My goal with twitch as a junior developer is to talk with people in the chat during my live to improve my skills and if there is youngest developer than me, I love to explain :)

We should share our channels and tips somewhere