The gain is portability. I do this between repairing family machines. You can take your OS and near m.2 mobo speeds and get to work. Live USBs are needed sometimes but having what's yours when you need it exactly where you need it is what matters in times of getting shit done.

Hear hear. It's just my laziness 🤣

That's what I do. I upgraded the SSD in my Steam Deck to a 1tb (before the prices went nuts, thankfully) and then ended up with a spare 256gb drive. I put it in an enclosure and installed NixOS on it as a sort of second system. It doesn't really do anything super important, it's more a learning project to get comfortable with NixOS without interfering with my daily driver. I could have just as easily done it in a VM but what can I say, I'm a tinkerer lol

Also the smaller OS's (puppy linux, tailOS) that can run entirely in RAM are going to be fast when it comes to anything but disk reads.

In such a scenario, do I create mount points for them or is there some other, preferred way of pointing to them? Symlinks?

Interesting! Never thought of that, even though I am running three RPis 😅 I do have a micro SD card and a micro SD card to USB adapter... 🤔

Yup! I'm considering burning my config and distro to a CD-ROM. Impossible to alter on boot lol

My NAS happens to have a CD/DVD drive for some reason lol