I have been using Linux since the mid 90s and want to be able
to use a tablet. I can see that web browsing, gaming, reading
pdfs, etc, works well on tablets. But what about things like emacs,
LaTeX, ... ?

Sorry if this is an idiot question. But I read that the asus transformer
prime has a locked down bios, so I'm wondering whether it's even possible
to install (open source) software, as distinct from apps.

The asus appeals because of the keyboard. I basically need to be able to
enter large amounts of plain technical text rapidly. I'm used to emacs and
LaTeX but could live with a more basic plain text editor (like gedit) if
necessary.

Advice will be really appreciated!