Depends on your needs. The problems with DNS servers from ProtonVPN, Mullvad and so on is that they use their own filter rules and you can't castumize them to your needs. You can probably go much stricter with what you want to block if you use a DNS based adblocker where you can manage your own filter rules.
Do I need a DNS-based blocker with ProtonVPN? From what I gather, ProtonVPN has its own adblocking DNS servers.
Depends on your needs. The problems with DNS servers from ProtonVPN, Mullvad and so on is that they use their own filter rules and you can't castumize them to your needs. You can probably go much stricter with what you want to block if you use a DNS based adblocker where you can manage your own filter rules.