I do think that a dedicated article for the configurable DNS services + the self-hostable services would be nice (e.g. NextDNS, Adguard Private DNS, ControlD, Adguard Home, and Pi-hole)
I suppose the argument for splitting them, would be that people interested in one of the above services are seeking more than just a DNS server, we are drawn to these options because we want (1 )control and flexibility, and (2) insight/data/analytics/logs, so in a way these services address a different and broader set of needs than a standard DNS server.
I suppose the argument against, is that it fragments the DNS server recommendations, and might be a bit messy to disentangle (For instance a single company, Adguard, has a standard public DNS, a private DNS service similar to NextDNS, and a self-hostable solution similar to Pi-Hole)k
If it were me, I think I would either write one article, but make it clear that there are two distinct sub-categories, or separate it into two difference categories.