So the questions are: 1. Do those two formats work for the initial implementation?
Yes. We provide a stream-oriented format and one atomic-import format.
2. Is the default correct or should it be switched e.g. rather than specifying FORCE_ARRAY to get an array, something like FORCE_NO_ARRAY to get JSON lines and the JSON array is default?
No default?
Require explicit of a sub-format when the main format is JSON.
JSON_OBJECT_ROWS
JSON_ARRAY_OF_OBJECTS
For a future compact array-structured-composites sub-format: