I didn't find many comparisons between the two let alone a recent one. So they're both packages for changing Firefox prefs for better performance and or privacy. I'm interested in applying them to Zen Browser. Can you provide detailed comparisons and if I should you use both?
Zen already makes use of a lot of Betterfox tweaks as I remember.
I don't believe you can use both as they both modify the same files, and would overwrite each other.
Arkenfox is geared more towards privacy at the expense of usability, so sites will break a lot more often. And there's no easy way to turn it off for only 1 site.
Personally after trying Arkenfox in the past, as well as Librewolf, it's just far too much effort dealing with the sheer amount of sites and features that stop working properly.
I'm with you. I appreciate Librewolf for what it is, but to me it's just annoying by default and I've also settled recently with Zen. It has even made me get used to using vertical tabs for the first time.
Both of them are very well documented with sources and explanations in the comments. You could pick and choose what you need and understand to create your own. Speaking from experience, using these prefs without knowing what they do might cause you a headache down the road when something breaks.