Hello there,
I would recommend checking this out:
https://en.wikichip.org/wiki/mirc/introductionThe wiki is the most up-to-date place, where many people contribute to adding documentation and examples.
Q: Does mIRC reload scripts "live"? If no, how can I make it to do so? Manual section on `/load` function does not mention this.Yes, if you modify your scripts within the native script editor all those changes will be "live". There is also
mSLDev (kind of out-dated, but great), which has syntax highlighting and more which also allows you to have the scripts "live". If you use an editor like VSCode, there is an extension under construction
mSL VSCode Extension (
GitHub Repo). This last option does not have a "live" option yet, but you can create your auto re-loader with a timer and checking timestamp changes. mIRC also detects changes and asks if you would like to reload said file. All files must be loaded manually, but you can code something to do so for you.
Q: Am I supposed to put a new script under "..\AppData\Roaming\mIRC\scripts\" and it will be used automatically or there is another file where the script shall be included?You can put your scripts any where, but the default path is the one you mentioned. You can load your scripts using: /load -rs "path\to\script.mrc". As previously mentioned all scripts must be loaded manually.
Q: Is there a "main" script repository? GitHub anyone?..No, there is no "main" script repository. There are few sites that host script repositories, such as
https://mircscripts.net/ (currently down tho). We do have a GitHub mIRC group called
mIRC Scripters (new members welcome). There are few GitHub repositories with various scripts out there which you can find with a search.
Q: What is the purpose of `users.ini`? Manual mentions it as "users file" and that is it.The file stores access levels, which are used to limit/control access on certain events. You can read more about it on
https://en.wikichip.org/wiki/mirc/access_levels 
