Links to Department Groups?

Is there a way to link to a Department Group? Or at least display products that fall under the Departments in a Department Group? I’d like to do this without using Themes as I was told if I create just 1 Theme, many automated populations will not work anymore…

Still would like to know if any of this is possible. I did find out that Related Items are NOT automatically generated, so I have to use Themes to populate them.

Curiously enough, I was contacted about being a guinea pig for a new Related Items system. No idea what the difference is… So can somebody also explain more about how the Related Items feature(s) work?