Hello lottsns,
I do not know if there is an existing visual - but I went ahead and threw this together quick to give you a basic understanding of how it works.
Commonly people also install PXE reps on their Preferred servers as well.
Note - if you have a DFS in your environment - you can also use that instead of using preferred servers for your packages.
Hope this helps to give you a basic overview visually.
-Peter