My biggest gripe with Vivaldi is that the first option when right clicking a link is to open in new tab and focus it. This seems like a small issue, but this is different to all major browsers which has open in new _background_ tab as the default option. There is 10 years of muscle memory for me to overcome to switch and I just can't do it.
Just checked, you are right! The issue was actually that it focuses the tab when you open it, it does not open it in the background. I have clarified the comment, thanks!