Most Accurate Document Class

We are mapping our documents to LOINC and I would like clarification on document classes within the Doc scale. When is it appropriate to use DOC.CLINRPT, DOC.MISC, ATTACH.GENERAL and ATTACH.CLNRPT? There are instances, (e.g. Autopsy Note), within our document repository that would map more accurately to a component within ATTACH.CLNRPT than any component within DOC.CLNRPT.

I think these column are important for billing. Some are used as claims attachment.

So I would ignore this classification into (DOC.CLINRPT, DOC.MISC, ATTACH.GENERAL and ATTACH.CLNRPT) and if a concept is a fit - why not use it.

I have a related question. I am unclear about the use of the document ontology with respect to mapping pathology results

Can someone explain the difference between

33721-2 Bone marrow Pathology biopsy report and 66119-9 Bone marrow Pathology biopsy report Narrative?

Which code would one map the actual report data to?

My understanding is that codes with a scale of DOC identify the type of attachment and populate OBR-4 and codes with a NAR scale in this case would represent the actual result and thus populate OBX-3?

Thank you.