Unless something has changed dramatically, the Firefox team (and other teams) test and fuzz Firefox extensively - obviously default prefs and features will get more coverage.
An actual fork like LibreWolf that adds or removes code and ships a different build fundamentally changes how the software is built and invalidates a significant portion of the security work that has been done by the Firefox security team.
I am not arguing that Librewolf or any of the other forks of Firefox[1] are necessarily worse for security, just that browsers are ridiculously complex pieces of software and making claims about security requires more than just gutting or adding features.
[1] other than Palemoon, because screw those guys; when I challenged them on the security program for Palemoon, their loopy leader tried to harass me and other former Mozilla folks. Given their propensity for instability I wouldn't trust them at all.
I should have rephrased my question to: "How do the levels of privacy/security/speed differ between Firefox+Betterfox and LibreWolf?"
I'm sure both have their tradeoffs, but I was just curious if anyone has tried and extensively compared both.
Betterfox is for everyday use cases and should rarely cause site breakage. It also has prefs to prevent annoyances and improve browsing speed.
this is a set of parameters you adjust in firefox..
So, the question is about comparing the settings on both.
Settings for libre wolf are here, https://gitlab.com/librewolf-community/settings