I don't think there is any other option. If those are very simple websites, there are some wp plugins that allow you to map them to domains, i.e you can use a single instance of WordPress and map the content to different domains. One plugin for this use case is WP Landing Kit.
That's a very good question. In WordPress, Full Site Editing (FSE) allows you to design your entire site—including the header, footer, and everything in between—using blocks. Blocks are the components for adding content in the new WordPress block editor, enabling you to easily incorporate text, images, videos, and more.
For this new approach, your site will require a Block theme, designed specifically for compatibility with this new editor. Also, one thing to note here is that the traditional theme customizer is no longer present in this environment.
Instead, FSE allows direct manipulation of site elements within the WordPress Block Editor
interface.