Are the privacy features (blocking of Trackers, Cookies, Cryptominers, Fingerprinters) of Firefox 69.0 complemantary to PrivacyBadger? or do they interfere with each other?
Firefox' new Enhanced Tracking Protection (ETP) does in fact the same what PrivacyBadger does, It blacklists Cross-Site trackers, blacklists cryptominers (although I'm not aware of one), so there is no need to use PrivacyBadger longer. Furthermore you can disable or allow third-party cookies. If you want to use PrivacyBadger anyway then I recommend Browserprivacy set to 'normal mode' otherwise there is a possibility whereby PrivacyBadger features can conflict with Firefox' new features since these protections only apply with Browserprivacy set to strict-mode. Privacy Badger does protect you against canvas-based fingerprinting, Firefox does this also and thus there is a possibility that both can conflict with each other. 1
Two security-guards that do the same is worthless and likely will override the existing security.