As a package provider, you should make sure that your users will be served best according to their intentions, and keep in mind that a system might be used by more than one user, with different preferences.
There are people that prefer the built-in Emacs modes for editing TeX files, in particular plain TeX users. There are various ways to tell AUCTeX even after auto-activation that it should not get used, and they are described in Introduction to AUCTeX.
So if you have users that don’t want to use the preinstalled AUCTeX, they can easily get rid of it. Activating AUCTeX by default is therefore a good choice.
If the installation procedure did not achieve this already by placing auctex.el and preview-latex.el into a possibly existing site-start.d directory, you can do this by placing
(load "auctex.el" nil t t) (load "preview-latex.el" nil t t)
in the system-wide site-start.el.
The --without-texmf-dir option can be convenient for systems that are intended to support more than a single TeX distribution. Since more often than not TeX packages for operating system distributions are either much more outdated or much less complete than separately provided systems like TeX Live, this method may be generally preferable when providing packages.
The following package structure would be adequate for a typical fully supported Unix-like installation:
Style files and documentation for preview.sty, placed into a TeX tree where it is accessible from the teTeX executables usually delivered with a system. If there are other commonly used TeX system packages, it might be appropriate to provide separate packages for those.
This package will require the installation of ‘preview-tetex’ and
will record in TeX-macro-global
where to find the TeX tree.
It is also a good idea to run
emacs -batch -f TeX-auto-generate-global
when either AUCTeX or teTeX get installed or upgraded. If your users might want to work with a different TeX distribution (nowadays pretty common), instead consider the following:
This package will be compiled with --without-texmf-dir and will
consequently contain the ‘preview’ style files in its private
directory. It will probably not be possible to initialize
TeX-macro-global
to a sensible value, so running
TeX-auto-generate-global
does not appear useful. This package
would neither conflict with nor provide ‘preview-tetex’.