https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/
QuoteOpen tabs, websites, and links in automatically managed disposable containers. Containers isolate data websites store (cookies, storage, and more) from each other, enhancing your privacy and security while you browse.
...
Easily open disposable containers that isolate attached data and are deleted after usage: Fully automatic, based on navigation-target, for certain websites, with configured mouse clicks on links or just by using the toolbar icon.
OOoooh, I love a sandbox!
That's nice. I found the multi-account containers and all that confusing when FF rolled it out (I still find it confusing). But this is straightforward. Easy to use and scratches an itch. I end up opening a lot of things in Private Tabs, but I think this is better... right? Is it?
my question answered in detail here
https://github.com/stoically/temporary-containers/wiki/Comparison
TL;DR - yes, this is better than private tabs
added: and here: https://medium.com/@stoically/enhance-your-privacy-in-firefox-with-temporary-containers-33925cd6cd21