Main difference to casual users will be extremely slow UI (running javascript code). Closing tabs, going full screen on YT - those operations can take over 1 second.
This is Vivaldi in action https://www.youtube.com/watch?v=-uCA2qIIG1M
This is Vivaldi in action https://www.youtube.com/watch?v=-uCA2qIIG1M
It's a great browser with lots of built in features. You don't have to use (or trust) more extensions. But too slow and overwhelming with all the shortcuts and features.
The worst part is Vivaldi devs dont see a problem. 16 core 4GHz Ryzen with 32BG ram and some UI actions still take ~ second :/ all because UI is naive single threaded javascript.