@Zalex108, it's just a "Thank You" post. Everybody is welcome to give their thanks here, I guess, if Vivaldi works for them in some way.
I think I could come up with a better title, though.
Just for completeness, my solved pain points in the order of importance:
Google Meet would constantly crash the browser on tab sharing; Wayland fractional scaling: everything is crisp now; Video acceleration didn't work; Custom compose sequence didn't work (fixed with --gtk-version=4); Vulkan didn't work on Google Maps, and it gave a noticeable speed-up now.I believe that was a joined effort of people from the whole stack: from the kernel, the drivers, to Fedora OS components, Chromium and Vivaldi.