For static sites Forestry.io is good. The editor experience is great and you can do clever stuff with front matter - including adding a component based layout builder.
https://forestry.io/blog/blocks-give-your-editors-the-power-...
https://forestry.io/blog/blocks-give-your-editors-the-power-...
The UI for these starters doesn't show off advanced stuff, but click on "Front Matter" and add complex fields/groups/blocks to get a feel for the UI.