There's some white space between the header template part and the next block which is the site title.
This is partly due to the unwanted paragraphs in the inline CSS for the header.
There's already a fix but it's not in Gutenberg 10.4.1

I tried Gutenberg Nightly but that had its own problems.

Workaround

• Copy/cobble the override logic from fizzie and/or sb.
• Add some CSS overrides in style.css