Asset Bundles - Best Practices / What's compiled?

I currently have a single unity project with arenas, textures, sounds, characters, etc. I need to use asset bundles to piece that out a bit.

The characters themselves will be released periodically so it seems like a good example to think of structuring the asset bundles.

I can associate gameobjects to asset bundles. I can then create and load those asset bundles in (thanks Unity tutorials!). That all works great but that seems more of just "how to do it" then best practice.

So should I have all of my assets (in this case character assets) in one large project while then associating individual character prefabs to asset bundles?

Furthermore, if I did associate a given character prefab to an asset bundle in the primary project, does that mean when the primary project compiles it will NOT include anything associated to an asset bundle within that compilation?

Also, should I be structuring the project in this manner or should asset bundles be done in a completely different project and then when the unity editor compiles the primary project, we load in the asset bundles even when testing?

Thanks