I wanted to go all in on Full Site Editing for a client project. But because of time constraints I ended using GeneratePress again. It's a great theme. Before navigation areas, template parts and global styles are really stable, I feel it's better to stay with a solid theme (like GeneratePress). But it will be January soon and I'm sure with WordPress 5.9 and TwentyTwentyTwo theme a big step will be done.

Wpdraft, a theme and plugin also gives some insights as what's a potential way to quickly design in WordPress.