You can use the db.collection.insertMany method for inserting multiple documents into a collection.
I dont think there is any specified limit for the input document array - it can be 10000, or 100000 or 1000000, etc.
See Execution of Operations on details about how MongoDB groups the documents into smaller batches when inserting many documents.
It looks like you had linked an older version of MongoDB v4.0 documentation - the current version is 5.0 (and my above links for documentation are for 5.0).
Yes, the individual document size limit is 16 Megabytes.
In MongoDB. there are databases, and collections within a database and documents within a collection. The 16 MB limit is for each document.
When you do a insertMany the array passed as an argument to the method holds multiple documents - each array element is a document. The dividing into smaller groups is the number of documents.