module+ sub-modules vs separate files for internal encapsulation

Encapsulation Strategy for Internal Definitions

When designing a Racket application that requires strict control over internal definitions, the goal is to ensure that private logic remains inaccessible to other components unless explicitly exported via the provide form.

Two documented approaches exist for achieving this boundary: using the module+ form to create sub-modules within a single source file, or utilizing separate file-based modules. While both mechanisms restrict visibility, they differ in how they handle architectural decoupling and interaction with the Racket REPL during development.

The primary constraint is maintaining a clean separation of concerns without introducing unnecessary file system overhead, while avoiding ambiguity during interactive evaluation in the REPL.

• module+ allows for rapid grouping of internal logic within one file.
• Separate files enforce a harder physical boundary between components.

Which approach is more sustainable for maintaining long-term architectural decoupling? Does the use of module+ introduce specific risks regarding active module context during interactive evaluation compared to separate files?