Unfortunately, doesn't really matter what browser you use. The JS APIs to harvest data are part of all major browsers now.
To which API are you referring? Mozilla, so far as I know, tries to protect the user.
Almost all web APIs can be used to fingerprint user (but Mozilla is reluctant to add new ones indeed when the ratio benefit/risk is too low). https://amiunique.org/
Lots of APIs are used to track users, but for example the Canvas API. Firefox also enables quite a few telemetry options by default.