Maybe you were using just the simple functions that any browser have.
In my case I heavily personalized Opera 12, and I just can't find another browser able to do everything I normally do with this...
for example I tried Firefox, I added like 35 plugins just to have the basic functions Opera 12 has, but using like 600Mb more RAM for a page... and also in the last versions I had to add a "not show images" button WITH A PLUGIN !! And I didn't even searched a simple way to disable webfonts or using custom CSS for pages... Damn, they are removing everything...
In Opera 12 you can modify almost every single menu entry of the interface from a text file, (you want a "edit this page with that unknown editor" choice when you right click a page ? here you go, or "send this link to the pandora to download" while surfing from the PC) and you can also have different profiles for keyboard or mouse shortcuts... you can filter all the links in a page and download them all, integrated adblock, integrated html/scripts/styles debugger and I can go on forever... It just don't need PLUGINS
Anyway Vivaldi Browser is just another Chromium child, so it will never be so customizable, or made with primitive functions that can be combined to create complex macros, but I have fate in the ones that made Opera great, maybe they will be able to think about something...