Personally I build Firefox from source and maintain a set of patches largely based on these: https://aur.archlinux.org/packages/firefox-esr-privacy/
If you're looking for a browser with first-class vim compatibility qutebrowser is outstanding.
I've also found palemoon to be a perfectly boring/stable/functional variant of firefox without all the drastic/breaking changes (vim plugins work quite well also)
Pale moon is not as good as waterfox, at least for me.
No, it doesn't show PDFs or videos, but does that belong in the browser anyway?