Seems it didn’t do any type of safe search for me

What wasn’t accurate?

Wouldn’t searxng run into that same issue though? Its just aggregated SEO instead of a single SEO source

How did you determine that? They specifically state there are no ads per their terms of service.

You can have both. One offers encryption, the other offers verification to avoid spoofing. Most domains have not implemented it with their dns settings and domain registrar though. As a result, NextDNS doesn’t enforce it for compatibility reasons. They would block 99% of the web if they required it.