Chromium is so bad….
Sadly, Vivaldi uses chromium, which is simply inferior. Text bounces from blurry to mostly crisp, video rendering issues, and so on. It's sad that chromium is used, other than the inability to use the browser consistently it''s pretty fast and clean. I suppose I'll stick with my old Opera browser. It's slower, but it has mouse gestures and rendering is always sharp and crisp. Until chromium becomes reliable, Vivaldi will be lower tier, which is too bad. Unfortunately, there's no way to fix the issue. I wish the Vivaldi team all the best, maybe chromium will get its act together some day.
I don't like Chromium either—never have, ever since I was an early adopter—but it was the best option available to the Vivaldi developers at the time they commenced development.