All of these offer something very interesting:
Access to (basically) all Linux-capable software, no matter from what repo.
Both NixOS and blendOS are based on config files, from which your system is basically derived from, and Vanilla OS uses a package manager apx to install from any given repo, regardless of distribution.
While I've looked into Fedora Silverblue, that distro is limited to only install Flatpaks (edit: no, not really), which is fine for "apps", but seems to be more of a problem with managing system- and CLI tools.
I haven't distro hopped yet, as I'm still on Manjaro GNOME on my devices.
What are your thoughts on the three distros mentioned above?
Which ones are the most interesting, and for what reasons?
Personally, I'm mostly interested in NixOS & blendOS, as I believe they may have more advantages compared to Arch;
While I’ve looked into Fedora Silverblue, that distro is limited to only install Flatpaks, which is fine for “apps”, but seems to be more of a problem with managing system- and CLI tools.
No. Your understanding to Fedora Silverblue is wrong. I can just run rpm-ostree install package.name in Silverblue, like other Fedora spins. The small disadvantage is that I need to reboot to apply this update. (re-construct)
but doesn’t that result in new A/B snapshots, or something like that?
Well, you can call it snapshots, but there is no need to think about it. In most cases, the system points to the newest snapshot (deployment 0). If a rollback is needed, I can pin to the older deployments. When a major change is to be applied (Like bump Fedora version), I'd manually mark the current deployment as dont-auto-delete.
Sure, but I’d like to have a more seamless experience, i.e. not having to open/start any “containers” or something like that.
I never used toolbox in my Fedora Silverblue system. I feel that I can't tell the difference between using Silverblue and the default Fedora spin
It depends on if the changes needs it or not. You can set a reboot flag on a given task and at the end the system will reboot, but if no reboot is needed then it will just make the change live.