Hello,
We have only Elementor version of the headphones demo. You can edit that page using Elementor page builder only. You can keep 2 page builders enabled on your site but it will slow down the page speed. And you can edit page using only that page builder that was used to create page content. Mean that you can’t use WPBakery to edit the Elementor page.
You can add Buy now button using the button element with any page builder and add the link you need for that button.
Regards