Second this - you can indeed use HDD and Qubes will work fine. For what
you describe it will work well.
You wont need to *make* a cup of coffee while opening a new qube, but
perhaps *take a sip* .
A while back I posted comparison times between SSD and HDD, RAM - you'll
see that the HDD is slower but works
Incidentally, working off USB is (relatively) fine. I have a few sticks
including a live Qubes that runs in RAM and they all perform fine. For
your use case dont exclude that.
unman