Firefox with Dark Reader, uBlock Origin, BitWarden and the about:config altered on several key issues not usually mentioned here. WebRTC, saved sessions, couple other things)
I am a Vivaldi Ambassador but when I use Vivaldi I am using it for specific purposes. I have both stable and snapshot versions but use them for different things. Opening up either Vivaldi opens up a preset of multiple web panels, extensions (those mentioned in Firefox plus 3-9 others depending on which Vivaldi I am using), pinned tabs, and several tab stacks grouped into relevant sites, PLUS Vivaldi has a setting which allows any browser tabs you had open prior to open once again.
Some people call Vivaldi bloated for the reasons I just mentioned. In my eyes that bloat is a feature, not a bug. When I open Vivaldi it is for specific purposes. When I open Firefox it is just to browse. I want my default browser to be fast to open. The way I use Vivaldi causes it to not open fast but that is by design.. opening Vivaldi for me opens up anything I am working on the way I want to be working on it.
That said I would hope that Gnome continues building on Gnome Web. I would prefer to use that browser but found that every tab opened exponentially made things slower.