The solution you gave me didn’t work on the long run, (I use Youtube and TED videos a lot for my work) but I broke my system with tinkering and put back a Timeshift snapshot from before the Vivaldi update, updated the system and Vivaldi performs without problems.
vivaldi browser 2 is out - beta testing here
Vivaldi package is removed from Antergos Repository, as priority on more needed stuff to work on.
May we will provide vivaldi package at a planned community Repository.
For now get it from AUR or add herecura unofficial Archlinux Repository to pacman.conf.
He do not have vivaldi-widevine package
at his repo so if you need get it from AUR.