Breakdowner works by utilizing a collection of objects for creating previous and future frames of your character. 

These are mesh-able objects with a material that are stored within a new collection which is linked to your scene's master collection.

The material is generated on-the-fly and is designed to work with eevee in both Material Preview and Rendered mode.

Yes, Breakdowner simply requires a collection of objects. 

This collection can be local, linked, and even nested within a character's collection which is linked.

Because Breakdowner generates objects which are added to the scene. This ultimately depends on how many objects (and the detail of those objects) are being utilized by Breakdowner.

To ensure performance stays optimal, Breakdowner utilizes blender's bmesh API for generating and combining multiple objects into a single new object, for each frame (previous/future). This reduces the overall load and keeps your scene minimal and compact.

Breakdowner's generated material pushes optimizations even further by being specifically designed for performance and sharing itself across all objects which are generated by Breakdowner.

If your scene can handle your own rigged character at a satisfactory result, Breakdowner will be unnoticeable.