rg90 composer require <package> and composer remove <package> only downloads the files and updates the vendor folder as well as composer.json / composer.lock. It does not do anything to the database.
When an extension is enabled from the admin panel, that's when the database tables and columns are created.
The database changes are not reverted when you disable an extension from the admin panel or remove them with Composer.
To revert the database changes, you have to click the "Uninstall" button in the admin panel on a disabled extension. That button "uninstalls" the database and deletes the data (but it doesn't remove the extension itself, Composer has to be used for that).
Generally extensions don't delete their own settings and permissions when "Uninstalled" so those will stay in the database even if you click "Uninstall" and remove them.
