The main goal of referencing thought the files is not in memory saving, but in saving your time in production. Let me explain.

For example, you make a movie with a character, which acts in 10 scenes. You've made 9 scenes, and in scene number 10 you've realized that something should be changed. If you just copy character from scene to scene - it would be a painful task, because you have to make this change in 10 separate files. But if your character is located in a separate file and linked into 10 scenes, it would not be a huge problem. You can just change character, and it will be updated in all 10 scenes.

To make this reference - simply pack your objects into collection, save file, and in the other file use File ⇾ Link to make a reference to the collection. Then collection is loaded, you may also click Object ⇾ Relations ⇾ Make library override to get the ability to move armature bones.

The main goal of referencing thought the files is not in memory saving, but in saving your time in production. Let me explain.

For example, you make a movie with a character, which acts in 10 scenes. You've made 9 scenes, and in scene number 10 you've realized that something should be changed. If you just copy character from scene to scene - it would be a painful task, because you have to make this change in 10 separate files. But if your character is located in a separate file and linked into 10 scenes, it would not be a huge problem. You can just change character, and it will be updated in all 10 scenes.

To make this reference - simply pack your objects into collection, save file, and in the other file use File ⇾ Link to make a reference to the collection. Then collection is loaded, you may also click Object ⇾ Relations ⇾ Make library override to get the ability to move armature bones.

Referencing may be memory-efficient, if you use the same object in the scene. Take a look at this example: The grass on the right uses a bunch of objects that's duplicated across the field, while grass on the left is simpler, but every strand is individual:

This allows to save a lot of memory and decrease the render time.

The main goal of referencing thought the files is not in memory saving, but in saving your time in production. Let me explain. For example, you make a movie with a character, which acts in 10 scenes. You made 9 scenes and in scene number 10 you realized that something should be changed. If your character is located in a separate file and linked into 10 scenes, it would not be a huge problem. You can just change character, and it will be updated in all 10 scenes.

To make this reference - simply pack your objects into collection, save file, and in the other file use File ⇾ Link to make a reference to make a link to collection. Then collection is loaded, you may also click Object ⇾ relations ⇾ make library override to get the ability to move armature bones.

The main goal of referencing thought the files is not in memory saving, but in saving your time in production. Let me explain. 

For example, you make a movie with a character, which acts in 10 scenes. You've made 9 scenes, and in scene number 10 you've realized that something should be changed. If you just copy character from scene to scene - it would be a painful task, because you have to make this change in 10 separate files. But if your character is located in a separate file and linked into 10 scenes, it would not be a huge problem. You can just change character, and it will be updated in all 10 scenes.

To make this reference - simply pack your objects into collection, save file, and in the other file use File ⇾ Link to make a reference to the collection. Then collection is loaded, you may also click Object ⇾ Relations ⇾ Make library override to get the ability to move armature bones.