The part that I'm a bit confused is this paragraph:

Unlike immutable distributions that lock you out of the native package manager and force you into sandboxes, Plutonium-239 keeps the core Arch experience intact. You still get the bleeding-edge Arch repositories and the power of the AUR but all of that with a 5-20% performance boost from a heavily optimized kernel and the peace of mind of an unbreakable safety net underneath.

And then the follow up:

Edit: if you look up how Fedora Silverblue works, it's pretty much the same, just applied to Arch!

It sounds a bit contradictory. Can we think about Plutonium-239 as of SteamOS that is classic atomic distro and based on Arch or this is more of a case to something like the RakuOS?