The Free Edition of PBXSync will synchronize Asterisk configuration files, but not information held in SQL databases. So your Asterisk configuration files (in /etc/asterisk) will synchronize and the nodes will work properly, but if you edit the configuration through FreePBX on one peer you will not see these changes appear in the GUI of the other peer.
To synchronize the SQL database you will need a commercial unlimited edition of PBXSync.