And then each tab is an app or app document window. So I could have a Chrome tab next to a Firefox tab if I wanted. Browser tabs would be peers next to other apps.
None of this is about security, or running apps in the browser. Just using tabs as the main concept for everything, rather than windows.
It's funny, my version would probably just put every browser tab into a different window and just use a powerful window manager like i3 to deal with everything.
These should at least get you pointed right.
There's no elegant way of telling Firefox to never use tabs, always open a new window. There are some extensions pretending to this, but the experience is terrible. There actually is a new tab created which is then detached.
I don't usually use Chrome, so I looked up wether it handled this, but it seems to rely on extensions too.
Qutebrowser works, but it has other limitations, such as poor extension support.
I've settled on NoTabs Firefox with a userChrome.css that hides the tab bar until Firefox someday supports native no tabs.
Using two large monitors is bad for your neck.