Not only can Tailscale directly integrate with NextDNS and therefore not require extra configuration on-device for DNS, but you can use Tailscale ACLs to assign different NextDNS profiles to different devices (for example, a parental control profile to a kid's device or an Apple TV, or an IoT profile, etc)

I did not understand the use case here. Could you please explain further?

I have been using NextDNS for many years now, but I didn't get why I should use Tailscale.