Hi,
I may need to come back later to clarify this post when I have more time and
fewer distractions. I don't know your situation, but as the mommy of an
investigative journalist, I wound up balancing out the need for a modern
processor with Intel Management Engine to run Qubes and ultimately gave my
child an old Thinkpad X60 with no hard drive and a TAILS USB stick. She chose
not to enable persistence.
It is a very small advantage of GNU/Linux but one that makes my own life so
much easier to be able to install to an external USB drive and then boot any
hard drive I want from any of my computers (with the same architecture, of
course) that I want.
We frequently use WD Passports. There are WD greens in there, which aren't
the sturdiest in the world, so you'll want to make regular backups, but they
certainly are handy.
You can also just get an enclosure and use whatever kind of internal drive
you would normally choose. Desktop drives are bulkier and need to be plugged
in, but they work fine anyway and it's never been a big enough hassle to me
to justify a trip to the store or a search for a screwdriver.
HTH
I'm sure I'll have more to say when I've read the whole thread.