Settings files should be avoided wherever possible, the only truly acceptable place for a settings file is within a plugin that is designed to only run on a single website.

If deemed necessary, this file should be named settings.php and stored within the plugin root.

There is an optimisation argument for settings files as each setting requires being loaded from the database, on the other hand there is a security implication for settings files as it is very easy to accidentally commit this file to GitHub. Additionally, settings files require the maintenance of a template for distribution too.

The performance implication can be somewhat mitigated with using add_option, by default add_option sets autoload to true, meaning the options are retrieved with a single query at load and cached for the remainder of the call.

Settings should ideally be stored in wp_options using add_option() and a corresponding settings page should be added, either to Campus Settings or WP Settings.