Hi André,
Best practices for Boxcryptor Classic (1.x) is simply to have a backup of the configuration file (.encfs6.xml) located within the Boxcryptor Classic Folder as it contains the actual encryption key for the folder and all files. If you have the configuration file (and the encrypted files, of course) you can get Boxcryptor Classic up and running on any computer from zero by re-opening the existing Boxcryptor Classic Folder.
If you really want to preserve the settings of Boxcryptor Classic, you should have a look at the folder %LOCALAPPDATA%\Secomba_GmbH (usually C:\Users\{USER}\AppData\Local\Secomba_GmbH). It contains the settings for a Boxcryptor Classic installation in the "user.config" file.
Best regards,
Robert