Since the GreatFirefoxCertificateRevokeAllExtensionsObliteratedCollapse, I've been using Vivaldi.
A closed source browser was never going to be an option, although I used to love opera.
I do realize the Viv is a Chrome build...
Pros: it's light, fast, and has approximately 200 customizations in Settings. Faster and more responsive than Firefox. Pick a simple theme and it will look clean. Browsing extensions adequate.
Cons: these settings aren't necessarily intuitive and dialing this browser in takes a while. Took weeks to dial in the fonts and font sizes to my liking. Point of reference: I can do that in Raven/Budgie after an install in minutes. I did not find the Chrome store as impressive as the Firefox extension store. But I got all the stuff all the same, but different creators on some. Some ugly built-in themes here, pick carefully--unless you love hot pinks and oranges...
Verdict: I see no reason to go back to Firefox just yet. Firefox could be a resource-pig, and sluggish at times. Vivaldi is neither so far. In Firefox's defense it was mostly stable. So is Vivaldi so far---not wiggy at all.