I don’t really understand your use-case. A document is just a record of something. you can store different types of documents I the same collection but better to group related records together in collections and enforce a schema to keep things consistent.
Fir example you might have a Books collection for records about books. Attributes may included title, date published, number of pages, authors, price, etc.
if you need to add attributes later, like a ‘category’ field, you’d usually need to update your templates because your need to decide how you are going to display ‘category’ I.e. where on the page, what CSS class to use, etc.
for one-to-many relations, like authors, you can put them in an array in your document. Then iterate using #each in your template, to output them in a table or list for example.
If you can be very specific about your concern maybe we can be more helpful. My company has built a very large ecommerce system in Meteor with lots of complex documents. I highly recommend autoform and simpleSchema packages for projects of any size.