Can you point to anything specific that reduces the attack surface?
When looking at the "securefox" config, it does a bunch of strange things, like enabling embedded TikTok links (https://github.com/yokoffing/Betterfox/blob/443710b0738ebc8f...) and disabling UITour (https://github.com/yokoffing/Betterfox/blob/443710b0738ebc8f...) which Firefox uses to highlight menus and is only accessible by approved Mozilla domains (https://searchfox.org/mozilla-central/source/browser/app/per...).
It's a very strange mix of configs.
I haven't had a chance to dig though those configs yet, but disabling things like service workers, webgl, normandy/experiments, pocket, and webrtc would be a good start at reducing attack surface
Want a mix of speed and privacy, while retaining functionality? Use Betterfox user.js.
Want more privacy and security at the expense of site functionality? Use Arkenfox user.js.
Want Tor prefs but without using its nodes/relays? Use Mullvad Browser.
Want anonymity? Use Tor Browser.
Most of the preferences in this will actually reduce the target-able attack surface, and disable some features that could be footguns, but at the same time disable some optimizations that aim to reduce cognitive load on users (which in turns reduces the likelihood that mistakes will be made).