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
besides uBlock Origin,
Consentomatic automatically declines cookie consent notices. works very well.