My understanding is that Carmen can do many things ... however, the flexibility it offers depends on what the objectives required to be achieved (normally determined by the company) are.
It can be tailored from 100% company to 100% crew. There is therefore no universal answer to the query - it depends on agreement between the user area (cabin crew or flight crew) and the company.
Both have (sometimes) diametrically opposed objectives (min vs max work, etc). Not everybody can always win. Depending on the implementation, then different techniques will be most beneficial, imho - from feedback received at BA (LHR and LGW).
** speaking as a pilot **