Best Practices: Sharing a project

Hello ! I don't know what kind of changes are planned in "app/Config/" files, but I am afraid to change things in this directory. Simple examples: I have custom routes, custom classes loaded with "autoload", custom config variables in "App.php" like "$supportedThemes" / "$defaultTheme" (dark/light) or "$supportedUnitsSystems" / "$defaultUnitsSystem" (imperial/metric)... Conclusion ? I am "afraid" to update my app now :-D

All apps are not using a database (I created a Slack bot with CI4 for instance), and I don't want to create ini/json (or whatever) files to store app settings (that is what I do sometimes) when there is a "config" folder with many options... If these files and options cannot be used because updates will (potentially) overwrite them, then maybe it shouldn't be in the "app" folder but rather in the "system" dir (or anywhere else).

This thread is interesting. I would like to know how people are managing this, and hear some recommendations.