Dynamic Dropdowns and Create Dynamic array is for forms that have two select list menus (dropdowns) that have a parent-child relationship where one filters the other on the fly.
For instance an application where you ask people for the make and model of a car and when they choose the make you only want model options for that particular make to be available.
With one to one relationships you can just populate a list with the related table and update the id in the parent table directly. Intermediate tables and manage relational table options are only needed for one to many and many to many relationships.