Firefox is still the most secure browser you can get once you've beaten it into submission through hundreds of about:config changes. Last I checked you couldn't even fully disable service workers or WebRTC in chrome.
Not for most people. I deal with compromised/malware infested websites so my team has a document with over 600 entries that locks down as much as possible. Arkenfox is included in that and that should cover what most people need in terms of privacy. Firefox on my work PC has things disabled that most people would probably want like SVG, Wasm, JS, auto/form fill, saved passwords, searching from the address bar, reader view, mathml, browser.fixup, remote fonts, PDF viewer, etc.