I did try it out. I admit it was a very nice UI, and had a few extra features on top... but nothing worth the asking price. I blew through the free allowance in about a week and deployed Adguard home, which has been fantastic.
If you need remote access, Tailscale is a very nice solution. It's wireguard, but with a fancy UI on top. It makes it trivial to share your LAN services, including DNS, to all devices on all networks. It will even allow you to advertise a single subnet, then replace the configured DNS servers on your endpoint devices. Voila, adblocking on mobile devices with no more effort than hitting 'log in with google' in an app. Of course, the main selling point here vs NextDNS is that it will tunnel all of your LAN services, and allow you to tunnel all traffic via any node in your tailscale network for a secure VPN solution with a couple of taps.
Also, I don't recall if the Fritzbox supports a firewall rule to intercept DNS requests to other servers - an essential feature to catch sneaky traffic from a variety of IoT devices trying to bypass filtered DNS.