Hi @dan.duett. Thanks for reaching out with this question. I would love to hear what the community has to say about this topic, so I plan to keep this thread open for a while.
Here are my thoughts:
I think the way you organize your tabs completely depends on how complex your Custom Type is. For a very simple page type, you might not need to use any tabs other than the first one. Then as a type becomes more and more complex you want it to be easier for content editors to find what they need.
One of the first tabs I suggest is the "SEO" tab that you mentioned. I always suggest putting your meta title, meta description, canonical links, social cards, and such in this tab. Here is an article about how this could be modeled in Prismic:
For the Prismic documentation article pages, we also have a tab for Navigation. In this tab, we've put things like the Breadcrumb title, the link to the parent document, and the link to the sidebar for that page.
We also have a general Layout Custom Type for the docs. This is a pretty complex type, so we use a number of tabs to control the content for each section. It includes a tab for the site header, footer, global sidebar content, the user feedback form, and others.
I hope this helps and give some inspiration for how you can break up your types to make them more accessible and easier to use for your content editors.
Now I would love to hear from the community on this and how they use tabs to organize their content!