Here’s a way (on iOS 14) of combining a WireGuard VPN with a separate encrypted DNS resolver: install a DNS profile (https://encrypted-dns.party) or app (DNSecure, NextDNS, iVerify) and then remove the DNS server(s) in your WireGuard profile.
https://libredd.it/r/nextdns/comments/lzfbpw/mullvadnextdns_making_them_work_together/gq3pam8/