Hi,
I think you're asking "What is the difference between Guix and GuixSD", and you don't feel that the manual is clear enough about this. Is that right? If so, how do you feel the manual could be improved?
I'm not yet a Guix/GuixSD expert, but in a nutshell, it seems to me that the biggest difference between Guix and GuixSD is that by using GuixSD, you gain many of Guix's benefits (reproducibility, easy rollback, etc.) at the system level. If you use a non-GuixSD distribution, you can still enjoy the benefits of using Guix as a package manager, but you'll be using something else to manage the system itself (the installed bootloader, the installed kernel, all the services that launch at system start, etc.). Most likely, you will simply be missing out on all the nice features that GuixSD provides.
For what it's worth, I think the current structure of the manual makes a clear distinction between Guix the package manager and GuixSD the GNU system:
Section 7 is all about GuixSD. All other sections apply to GuixSD, too, in the sense that they discuss the Guix package manager, which is used by GuixSD. When necessary, the manual calls out the differences between doing something on GuixSD vs. doing it on a non-GuixSD distribution. Again, if you don't think this is clear enough, how do you think the manual can be improved?
I see that you are hoping to convince others to use Guix/GuixSD instead of alternatives. That's great! You might be interested in the following email thread, in which Malcolm Cook discusses his efforts to make the case for GNU Guix:
http://lists.gnu.org/archive/html/guix-devel/2016-02/msg00286.html
Good luck,