I see a lot of people implimenting different systems to give pages types. Systems like PARA, Person/Maggie Appleton's modified Evergreen Notes system, etc. Even within my own Roam Research graph I have pages for all types of things including:
People / businesses
Primary sources (books, articles, papers)
Questions / topics
Things (apps, emotions, completion statuses)
Many people append a letter or phrase at the start of a page to identify its type. While this may work with other platforms the linked nature of Roam/Athens makes this ugly when doing in-line page/block references.
The best solution I see for solving this is using attributes. If a page has attached attributes/metadata then filtering a search based on an attribute value would be trivial