The best of both world, a VPN service were we get to chose to apply our NextDNS config or use it on it's own without any DNS filtering.
And that's better than the other 929182 VPN services where NextDNS also works because...? On Android DoT setting works regardless of what VPN I'm using, Chrome and Firefox DoH also don't care what settings I'm using. Once popular VPN providers add the ability to define custom DoT or DoH for the tunnel, there will be no point for a NextVPN to exist.
Most of well known VPN services have an option to customize DNS based on the user's need. They don't recommend any customization though. Obviously for the sake of DNS leak, but they do offer the function. I know people who like to make the maximum possible Geo bypassing method by adding their customized paid smart DNS values on this field. This way the DNS itself opens any Geo restricted website while the VPN offers the competed anonymity over the web. In these VPN services (like XpressVPN) you can even add the Next DNS values, and it will work just fine.