Sandbox has been keeping itself up to date with WP versions for months now.
I have just uploaded the Green Path theme to see how it goes with the new system, and to get used to Gutenberg. Colors and header pic are deliberately wrong to keep me alert to the fact that this is the Sandbox, not the real site.
Featured image (wtf?) is an ant ~ 960px wide.
Okay … “Featured image” is a full-width pic *above* the post text and basic post info. I like it.
The Excerpt? Not so useful. Looks funny in Georgia, btw; better in italic?
The Logo appears above everything else and is quite big – 160 x 160 px. It pushes everything else downwards. It could perhaps replace the site title, but doesn’t look good as an addition to it.
The fonts which are showing up are Helvetica and Georgia, i.e., the same as in the real site, as they should be. They can’t be changed in the “Customise” menus.