Not quite. Silverblue is based around flatpak's (containers) and composing your OS from a set of containers. NixOs is based on Nix, which doesn't use container

Not quite. Silverblue is based around flatpak's (containers) and composing your OS from a set of containers. NixOs is based on Nix, which doesn't use containers but links binaries against specific versions of dynamic libraries to resolve dependency issues and allow for reliable installations.