The configuration files are the primary source of user-friendly settings. The config files need to be edited before NodeCG can launch and can be edited between sessions for various function changes. Data from config files are read upon the instance loading, meaning if you want to change any config settings, you'll need to restart NodeCG for them to take effect.
The files are in the 'cfg' folder in your package's root folder. There are eight config files: one for the overall package, one for the NodeCG dependency, and six for the additional bundles. The files are written in JSON, a JavaScript-based language for storing data. You can read about JSON's syntax here.
The default configs are provided on these pages, so if you make changes that break anything and can't recall how to undo them, you can copy and paste the default configs from here.