NextDNS for IPv4, DOH, and private DNS ping time, DNSBench (IPv4 only) benchmark, and no errors in Windows Event Viewer. The free tier drops to "no filtering" after the limit is reached, but basic ad and malware blocking seem to remain. The "adblock-tester.com" tests indicate equal effectiveness in the "no filtering" free options for NextDNS, AdGuard, and ControlD. For reliability, using NextDNS as the primary and AdGuard as the secondary seems to be better.
For my location, DOH and private DNS ping time are only 10 ms; the rest are 30 ms (except Quad9 and Cloudflare, which don't block ads). I only do IPv4 pings.