NextDNS (the resolver) is not equivalent to using an app (a client) like TrackerControl.
NextDNS (the resolver) cannot prevent apps from doing their own DNS, or prevent apps from connecting to preset IPs. Only if the queries reach the resolver can NextDNS act upon it / track it / block it.
Also, apps like TrackerControl can do per-app blocking, just like LittleSnitch / LuLu and Glasswire do on macOS and Windows respectively.