Here is a good starting point for understanding ADU attributes: https://www.blackbaud.com/files/support/guides/ta5/Iectv36/Setting_Attributes_for_an_Account_Data_Upload_Vendor_File_Code.htm

The preferences starting with “ADD” only affect whether to add or update, the matching logic will be unaffected. Also the TA help page specifies that these
 
“Determine whether uploaded name/address/telephones/email information should be used to make changes to existing records.” The data will be used for creating a new record regardless of how these are set.
 
However I want to reiterate that some other attributes do affect matching including the ones that start with “Unidentified”.
 
If do_updates is blank that will be considered the same as N.