Thank you @sgunhouse the second tab in Vivaldi prefs has this option to use native window. After restarting Vivaldi the title window gets its standard os x appearance back. Since I placed the Fav bar and the tool bar below the window, I found that color on the top (title bar) was a little too much.
On the other hand I find very handy the way the active tab is colored.
@sircasey It depends which OS you use. On osx the mute icon is on the right side, leaving the favicon untouched. If this is different on windows or linux, you can achieve this with custom css. Favicon right, audio left -- or audio right, favicon left. Shouldn't be hard to do.
All major text blocks in legible font with good contrast to a light background
The number of times I've come across sites and apps that insist on putting grey text on a white background (or worse, on a dark grey background and passing that off as a "night mode") is very disheartening.