For a one way sync there is a free application with a GUI named Carbon Copy Cloner. Although Carbon Copy Cloner is a visual interface around rsync, you don't need to have rsync installed as it is already included in the software package.

To sync with a remote Mac, there is the option to choose "Another Macintosh" as destination/target. Such a remote sync requires the installation of a 143 KB package on both the local and the remote Mac.

The sync is on demand/upon request or can be scheduled.

For a two way sync there is a free application with a GUI named Carbon Copy Cloner. Although Carbon Copy Cloner is a visual interface around rsync, you don't need to have rsync installed as it is already included in the software package.

To sync with a remote Mac, there is the option to choose "Another Macintosh" as destination/target. Such a remote sync requires the installation of a 143 KB package on both the local and the remote Mac.

The sync is on demand/upon request or can be scheduled. Though my guess is you need to create 2 jobs: one for each sync direction.