How to create a settings page in a separate module in yii2?

Question

Yii

structure
----application
-----users
----application settings
-----main settings ---> and here implement the settings stored in the database so that it is not like crud , but there is a table, values ​​and a button save, and if this can be implemented using crud, then how to limit the number of records in the table, and display in the view only one record already open in update