Phiqu I guess I get bored easy, I couldn't say why...I keep three dependable browsers around. Librewolf is one of them and fantastic, keep it. Vivaldi will be fun, too and it sounds like you know it very well. I like a Chromium knockoff and FF and a FF-knockoff personally.
"Epiphany had something."---it's a very special browser. It has that "something" for sure.
Of the weird inbred gnome browsers (Epiphany, Eolie, Midori
) only Web stands above. The rendering thing AFAIR is a cross between library compatibilities (webkit?), modernization, and lack of consistent upkeeping. This is really "a could have been something special light browser" and I've found nothing light to take it's place.
Falkon is quick and light and unattractive to my eyes, and the other two 'inbreds' don't really lack in features (they are light) but they lack in performance including rendering, font rendering, anything resembling consistency, etc.
Flatpak has a plethora of 'light' browsers (surf, otter, other stuff I forgot) but some don't even work. Agree with you on Epiphany though. I hate the Google/FF monopoly on browsers so Epiphany is kind of heartbreaking because it's not a day-in/day-out viable alternative right now.