ProtonVPN, DNS resolver, encryption and privacy

Good Morning, i hope you're all having a nice day ;)

i would like to have some clearer information about custom DNS.

So, running on android graphene OS, Which way to set up a third-party DNS is better for privacy and security using Proton VPN?

Is it better to set up nextDNS in the Private DNS settings of the Android device with a DoT address?

How is it better to just link the IPv6 address in custom DNS of ProtonVPN application?

I am wondering which one hides the DNS queries from the ISP?

As it would seems like that, If I use Private DNS setting from a graphene OS, nextDNS uses encrypted DNS resolver.

and that if i only link the ipv6 address in protonVPN custom DNS, the DNS queries or not encrypted by nextDNS and so visible to the ISP?

i need clarification and guidance to manage setting up those two for maximum security and privacy.

and a last question, would you recomande a custom DNS in the detriment of ProtonVPN NetShield?

( i am using NextDNS, becaue i want no google, and i have no social media )

thank you all and keep it rocking ;)