Hello
It is true that we have some examples that use Beaver Builder, though this is because it is free, not because it is recommended.
Builders cannot be used on any of the GD Templates or pages within the page content area because GD content is inserted into those page content areas by the plugin, and that will overrides all content including builder content. In some cases, when builder content is inserted into the pages, there may be a conflict and so the solution is to remove the builder content.
Builders can be used on the site front page or any other WordPress page, though, and each builder usually has some form of “insert shortcode” functionality to allow you to use GD shortcodes on other pages and posts without interference.
With Elementor, there are no specific issues, but certainly Elementor, as with other builders, should not be used on GD pages.