Open Link in New Tab - in the background
This should open the tab in the background by default no need for two menu items for this, All you need to do is have one menu item "Open Link in New Tab" then have the way it functions in the preferences if some like it to pop open immediately.
@Rustle It is much easier to press ctrl when clicking if you want to change foreground/background rather than having to change a preference!
Or use mouse gestures if you don't like the keyboard
Or you could click the link with the middle mouse button
@zaibon Indeed, it's that easy. It's true that more options are welcome in Vivaldi, but it took me one day to get used to what Vivaldi already offers in terms of usability. The option is already there but some don't want to get accustomed.