Opera gx is the fastest. But I don't like the look. I can't remember if I used Vivaldi on desktop but I remember not like the mobile app. Don't remember opera normal tbh. I didn't know mullvad had a browser. Chromium based I'm guessing?
Discussion
mullvad browser is tor browser without tor, so firefox with way more anti-fingerprinting measures
what he said,
it is what I use but took some customizing as it starts with enough privacy enabled to make it almost unusable as a daily driver (imo)
I looked at it. Seems great for private browsing but not a daily driver replacement at all. Edge has linting for common file types like json which is great as a dev. The dev console is also my favorite.