Hi there,
To add a wrapper around the posts, you can create two Hook Elements: https://docs.generatepress.com/article/hooks-element-overview/
The first would be your opening element, and would be added to the generate_before_main_content hook:
<div class="facets">
The second would be your closest element, which would be added to the generate_after_main_content hook:
</div>
Then you can use the Display Rules to choose where this element should be added.
I’m not sure about the query thing, as GP just uses the standard WP query. Have you checked with FacetWP on this?