I don't want my browser add-ons to make my fingerprint unique. How risky is it to add a password manager browser add-on? I've got Firefox and KeepassXC. Should I add the KeepassXC add-on to Firefox?

The Brave Browser has fantastic finger print blocking as it sends randomized information each time any service attempts to finger print your browser. Maybe start using Brave and forget about the issue? Its a chromium browser which by default blocks ad's and trackers too. I'd recommend increasing the tracking and fingerprint security in the settings though.