I would love the option of keeping containers in vertical tabs with “page tabs” horizontal. For example; Facebook, Personal, Banking, Work, Incognito, etc containers along the left as vertical tabs, and each one has all the pages in tabs across the top. Vertical tabs only appear after you open more than one type of container.
Workspaces. Vivaldi has this and it’s the only reason I use them.
Is each Workspace isolated like Firefox’s container tabs?
Not sure what that means. But you have workspaces that contain various tabs and you can’t access a workspace’s tabs from another workspace. I have workspaces for recipes, videos, programming, and gaming.
Firefox Containers are walled off from each other. No settings, cookies, trackers, etc. are shared between one container group and another.