The order goes like this, as this list increases, the later override the earlier Order inspired by https://www.npmjs.com/package/rc#standards

1. Each property has a default
2. userConfig from .boltrc.js that's in same cwd as where bolt was ran, unless they use --config-file path/to/.boltrc.js
3. Env Vars with bolt_ prefix; bolt_verbosity=1 will override config.verbosity - case matters!
4. Certain command line options like bolt build --verbosity 5 - not every config option is overridable this way. Run bolt --help or bolt build --help to see options.

For both 3 & 4, it doesn't support deep merges, so only top level properties.