Foundations Library and Custom Products

Please bear with me as we are in the process of implementing the new library and have some questions.

If we take a "standard" cabinet from the new library and customize it and then save it as a new product to our library, will it be overwritten when we do the monthly update?
OR If we modify a "standard" cabinet within the library and save the changes to the "standard" product, and NOT create a new product, will it be overwritten when we update?

Im trying to understand what products, materials, settings will be overwritten when we install a new Foundations Library Update each month.