I have made a lot of modifications of Ryan Wiemer's GCN Gatsby starter theme from the Gatsby website. I chose his theme since it had Contentful already setup with a blog and pages. There are also a lot of smaller libraries and plugins I use but styled-components is one of my favorites.
I use Segment and feed that data to Google Analytics and FullStory. I collect this information to get metrics of my site's usage and how it is being used. I use FullStory to identify UX issues and bugs. So, if you "rage click" (the universal digital signal of frustration), by click on something several times quickly then I get notified. By your use of my website, you agree to the necessary collection of this data. If you've got concerns, email firstname.lastname@example.org.