Disable multimedia auto-play on per-site and per-content basis.
Vivaldi should DO THIS FIRST, to one up the other major browser.
I bet it will surely turn many heads & make a huge name for Vivaldi if Vivaldi is the first browser to support this function.
According to this report https://www.macrumors.com/roundup/macos-10-13/ , Apple's Safari will allow for per-site/per-content preferences to enable or disable multimedia auto-play.
The idea (as opposed to implementation) has been so old that even(?) a main-stream browser has started to look at it as a mandatory feature rather than an innovation. . . .