This is a weak argument as pi-hole needs to go to a resolver or perform recursion itself which will give you the same latency or worse. The 1ms latency will only apply to already cached entries that are also cached by you OS anyways, whichever solution you are using.
If you configure NextDNS on a router, your router will perform the exact same caching pi-hole is doing, so it will make no difference performance-wise.
If you configure NextDNS on a router, your router will perform the exact same caching pi-hole is doing, so it will make no difference performance-wise.