In order to make the background slider for free, only using Elementor without other plugins, you should to do the following steps.
You can forget about searching for the most editable posts, pages or other post types. Just add them to a special sidebar in the admin panel with the Admin Quick Panel plugin.
How to choose a more suitable page builder for your WordPress project? A comparison of the multiple parameters can be found here.
Quite recently a new page builder was released. It allows you to edit the content of the drag and drop mode in the frontend. But where to get new themes?