Gatsby Preview gives you hot reloading of content. So you change something in Plone CMS, and it immediately is visible on your Gatsby site.
Plone CMS -> Web hook -> Gatsby source plugin. When content is created, edited, deleted, we will fire a websocket event.
When you change the title of a folder, you should update the breadcrumbs of the children too, and also navigation in several places. It took me a long time, but I have implemented this.
I have created a Gatsby theme for Plone: https://github.com/collective/gatsby-theme-plone