UIDocument mutilpicity/reuse best practices (how many of them)

I'm doing some research on the proper use of the "new" UI Toolkit for our new 2D game project. I wonder what the right way to structure the UI elements across the UIDocuments is (from the performance, manageability, and common sense perspective).

• Shall we use a single UIDocument(visual tree) for all VisualElements?

• Or is it better to create multiple UIDocuments for particular uses (e.g., Inventory, HUD, game menus, in-game chat, etc.)

• I can imagine the radical approach of particular game objects (weapons, keys, etc.) having their UIDocument (e.g., every draggable object has its own UIDocument for its 2D icon with a label).

Any thoughts?