imho as a reader a proper lattice (see concept lattice) is useful. Everything else is typically less helpful than it could be. I don't find network graphs like those usually produced by "second brain" tools that useful at all. Even Niklas Luhmann, who largely inspired this networked hypertext approach with his analog zettelkasten imposed enough structure through meta notes and special linkages such that browsing at a particular node could be more hierarchical latticeesque and directed. Browsing pure undirected networks is usually not super useful when it comes to fashioning structured understanding precisely because such an object almost completely lacks structure. Perhaps a set (sans any linkages) is perhaps the only other object with less structure than the undirected network.