Root, while more efficient, isn't strictly necessary. AdAway (FOSS, F-Droid) can run without root using the stock Android VPN backend.

RethinkDNS is implemented as a VPN service but it has support for local filtering combined with optionally using a WireGuard VPN or multiple chained WireGuard VPNs. You can have both via the VPN service API rather than choosing one or the other. No need for app accessible root access.

I use both adaway and AFWall+, as I don't like random apps making random connections, even if it's not for adverts. Once google play store ate my monthly data allowance, and it will never happen to me again.