Including Multiple JSX Scripts

I've encountered three methods:

1. //@include path/to/file-to-include.jsx
2. #include path/to/file-to-include.jsx
3. $.evalFile("path/to/file-to-include.jsx");

Some questions:

1. Is having multiple <ScriptPath> elements in the manifest file supported?
2. What is the recommended way to include multiple JSX scripts?
3. Where can I learn more about the ExtendScript environment - features beyond the standard ECMAScript implementation (e.g. this include stuff)?