The EFF is very good at what they do, and I’ve found it to be reliable, based on auditing traffic with tools like TrackerControl and AppManager as well. There is also resources noting test results such as https://privacytests.org
Not quite for me - Fennec (at least the build from F-droid) does not randomize fingerprint, AppManager and TrackerControl both show it has embedded trackers sending telemetry to Mozilla, and Fennec is not available on desktop. Librewolf is hardened Firefox on desktop, and is very good though, and has the trackers going back to Mozilla removed, but it does not randomize fingerprint.
This is the result of the default install of Fennec - it needs the user to install an extension to get ad and tracker blocking like you have