One of the things I use pi-hole for is to set customer DNS entries so anyone on the network will be redirected directly to the self hosted services when the type in the appropriate domain name. So it’s not just about the filtering (which I also want), but also the (network wide) custom DNS entries.
I’m also happy with simple. I’m not overly against keeping the pi-hole and gateway separate but was just wanting to know if combining them would be an option (which is sounds like it is, but not super easy).