Isolation is good for security reasons. Think of the Titanic design, if not the reality. Explain icebergs and compartments here. — that’s the ELI5 version

Also similar to “sandboxing” (MAC, SELinux). Libre Wolf is isolating tabs tailored to specific site interaction profiles like “banking” and “personal” which conserves security while also (ideally) preserving requirements needed to still interact with the site. See a similar project called Bromium.

https://www.bromium.com/wp-content/uploads/2018/06/Bromium_Secure_Browsing_Data_Sheet_EN.pdf

No. Firefox is not the most secure browser, although it is more amenable to privacy protections. Tor browser is based on Firefox but they are moving to Rust code. Chromium based browsers are supposed to be stronger, but then you’ve got to de-Google it if you want the privacy controls. Brave is good for that.

Libre Wolf is a hardened version of Firefox. No browsers I know of that are commonly used sandbox, containerize, or virtualize by default (like Bromium). So, containerization is a novel and cool feature. Otherwise, you have to use firejail profiles or SELinux. But the other important aspect is shaping the privacy protections of the browser to fit with the site you are interacting with. As most people know, things won’t always work on the net with all protections and security mechanisms in place. So there is a sweet spot that depends on what you are doing. That’s why I think Libre Wolf offers a useful innovation with this feature.