i use Quad9 in everything which has uBlock Origin as an available extension, otherwise NextDNS with OISD and/or Hagezi Normal. (hagezi pro broke some images for me which were not ads or trackers)
for a quick and easy set and forget ad and tracker blocking DNS, definitely Adguard. i set this DNS on my parents devices like phone and firesticks. i set the router DNS to Quad9 to serve as a phising and malware blocker for anyone on the network.
there is a Roku in my household which can’t have DNS specifically changed, so i have to use NextDNS for my router (Adguard would work too), though ideally i just want Quad9 in most places due to the Swiss law enforced privacy policy which promises no personally identifiable logging