Hello,
1/ WPBakery plugin styles and scripts make the section full width. So, if these styles and scripts are still loading you see the boxed layout. We can’t speed up this process from the theme side. You can just enable the site loader to show the site once the page is fully loaded (Theme Options > General > site loader).
2/ Read this article – https://xstore.helpscoutdocs.com/article/100-how-to-speed-up-my-website
and this topic https://www.8theme.com/topic/switching-from-bakery-page-builder-to-elementor/
Regards