How to protect DNS ip in some website DNS leak test

Hello everyone,

I’ve been looking into ways to secure my DNS IP and prevent leaks when using online DNS leak test tools, such as ipwtf.com. I recently came across NextDNS, which offers encrypted DNS (DoH, DoT) and privacy protection. However, I still see my DNS resolver in some leak tests, and I’d like to fully understand:

1. How do DNS leaks happen, and how does NextDNS help prevent them?

2. Can NextDNS stop EDNS (ECS) leaks that expose my IP range?

3. What are the best settings to use in NextDNS to avoid leaks in DNS tests?