Custom Post Types

What's the closest thing to WordPress custom posts types? Modular pages? Or is there another way that works a bit better for large numbers of repeated items with the same fields?

I think that article explains it the best: Grav Pages

Basically there are no limitations in Grav. Modular pages are a good showcase for how a custom twig file can render stuff from a page with custom headers. You are not limited to modular pages though.

You can use the modular pages/templates in the one-page skeleton as examples, but really this could be a regular page too. You can create any root-level .html.twig template file for your pages, and then reference this template file by your markdown filename

OK, great. Thanks guys!