Sorry to revive an old post but the warning/error still exists:
So at least the printcap name = cups line shall be in the [global] section. The global section is located in 10global. Do not recall if multiple global sections can be put on the same resulting smb.conf file, that could be an alternative to keep everything almost as is.
I don’t know, just spotted the error on the log of another user. Apparently it might only be used by legacy applications. Info is old but probably still valid:
Global parameter name found in service section
Indicates that a global-only parameter has been used in an individual share. Samba ignores the parameter.
CUPS does not need a printcap file. However, the cupsd.conf configuration file knows of two related directives that control how such a file will be automatically created and maintained by CUPS for the convenience of third-party applications. Legacy programs often require the existence of a printcap file containing printer names or they will refuse to print. Make sure CUPS is set to generate and maintain a printcap file.