That's right, this pair of modules allows for full node replication between Drupal sites over Atom!
There is no mapping table for received fields. Rather, CCK fields and taxonomy terms present in nodes represented in the incoming feed will be mapped to identically named CCK fields and taxonomy terms on the receiving side. Fields that are not present will be ignored.
That is, if you are receiving a node with a field named "field_bob", and the node type you've selected to save to in the Feeds configuration has a "field_bob" on it, it will be populated identically to the remote node. If not, that incoming field will be ignored.
File transfer is also supported! The Feeds Atom module will call back to the original site and download files stored in a filefield field as needed. There is also duplicate checking so that an incoming file that is repeated multiple times will only be downloaded and stored once, and then referenced multiple times. Hook-based implementation allows for additional processing to be added by 3rd party modules.