How deep does Blender file packing go?

Question

I recently (almost) completed a project and I am in the process of archiving about a hundred *.blend files having selected those used to ouput *.mp4 files for editing in Premiere Pro. I have gone through each of the "hero" files and selected File\External Data\Pack Resources. After everything is packed, I will remove all the extraneous incremental files and only keep the packed versions thus clearing hundreds of GB from my C:\ drive. I understand that packing should include all the textures and meshes, but I have many files that have other *.blend files appended and loads of particle systems as well - some of which have appended collections as the generator. During development, the directory structure grew to sixteen categories with as many as twelve subdirectories each of which could have four to ten subdirectories. There are also imported alembic files from other programs with their associated textures that are spread over two additional drives in various subdirectories. Packed files appear to find and include the textures properly, but...
My questions: How deep does Blender packing go? Will it include all the appended files? Will it included the textures, cameras, lights and animations from the appended files?? Will it truly create stand-alone files without needing any external resources? What happens with caches? Will they be generated anew if a packed file is opened and run? With so many files, it would be prohibitively time consuming to backtrack which collections have been appended into which "hero" files and even more time consuming to verify that each of the packed files opens and functions properly. Additionally, I do not want to keep all the hundreds of GB worth of development files available on an external drive in the off chance that some texture or collection is missing. But of course recreating some of those would be a real nightmare. I think I have all the *.mp4 files needed for the final Premiere edit, but some scenes may need to be extended or otherwise modified as editing progresses and music and effects are added. Any clarification or guidance would be most graciously appreciated!! Thanks in advance,

Answer 1

Appending and importing are static processes, ie they don't rely on the source files anymore, which means you don't need to worry about that data, it's safely stored in your file. Packing is aimed at data that's referenced externally, such as image and video files).

Linking on the other hand is dynamic, so if you linked in some data from another (source) file, this source file must stay around.