Oxygen is compatible with page builders such as Elementor, Beaver Builder, Themify Builder, Thrive Architect, Visual Composer, and any other page builder that controls the output of the function the_content() in WordPress.
To use Oxygen with page builders, create a Template from Oxygen -> Templates.
Design the template as desired, typically with a header and a footer.
Where you want the content editable by the page builder to be placed, use the Inner Content element. Go to +Add+ -> Basics, scroll down to Other, and select Inner Content to add it to your template.
All items rendered with this template will now work with your page builder. You may use the page builder to create content inside the Inner Content container.
Do You Need a Page Builder with Oxygen?
No, of course not. You can design your entire site with Oxygen.
However, one reason you might want to use Oxygen with a page builder is that maybe you already have built a site using a page builder, and you don't want to redo it all in Oxygen yet, but you still want to install Oxygen to replace your theme and take more control over your headers, footers, and other site templates.