Mullvad Browser is torbrowser without tor. Its basically the same as Librewolf, afaik Librewolf uses arkenfox user.js which is based on torbrowser.
But the Torbrowser has a “disk avoidance” principle, which means they always use “private browsing” mode as that never saves data on your hard drive.
This means it always deletes everything, session, cookies, tabs, searches, …
MullvadBrowser is not more private than Librewolf and ALSO has these things making it basically unusable for daily usage.
This may lead to people using it “for the private stuff” and a shitty browser for the rest. Which makes no sense, as Librewolf is the same.
And also, private browsing doesnt allow containers, meaning “multi account containers” and “temporary container” are nonfunctional. You dont need to run multiple damn browser sessions, just use containers.