Question: Will the plugins I’m already using continue to work?
Answer: It depends on how they hooked into WordPress.
Plugins such as Yoast SEO, Jetpack and WooCommerce should all continue to work.
Plugins which extend PHP server code which has been replaced by a different solution may not work.
For example, I used a plugin called Menu in Menu, which allows a Custom Menu to include other Custom Menus. It hasn’t been updated to work with Full Site Editing. So my menus need to be built differently for an FSE theme.