Anecdata: I've been using it for a couple of years and not had any concerns with speed. I don't know what faster would be. I occasionally have to use firefox or something else on corporate machines and Vivaldi doesn't seem any slower than that on any sites I visit.

I do use Pihole to get rid of ads so maybe that's a factor

I use Vivaldi and there are no speed issues except the initial startup time and new window launch time. Since I always have a browser open on my machine the initial startup time isn't noticed and since I use tabs+tab-groups the new window time also doesn't matter, but it is a real pain when I /do/ want multiple windows.