I develop courses in the framework as a stand-alone environment. In many situations, a single-width component positioned in a block without an accompanying contrib-blank component works just fine. The layout does not collapse.

1. When is the use of Blank necessary to maintain layout in (a.) while authoring in the framework, (b.) while using the authoring tool?

The use of Blank may be desirable even if the layout does not depend on it for issues of stability, etc. 

2. When is the use of Blank desirable (e.g., to achieve positioning or effects that cannot be achieved with CSS) (a.) in the framework, (b.) in the authoring tool?

Thanks for all insights!
Chuck Lorenz