This has been answered before: Mull vs Fennec. Mull has better defaults. Fennec isn’t called Fennec, actually it is Fennec F-Droid - it exists, because it is the older name for Firefox’s android app, which is now called Fenix, so to avoid trademark issues with Mozilla, they appended the “FDroid” sub-string to protect the DivestOS mobile browser project from any sort of infringement strikes - honestly, that logic makes no sense, because I still think that it infringes the trademark in a way, but now that the name is changed, it probably does not.