In Voyant the term plans = "what-if" scenarios (including the base plan).
The term client file = the client-specific case files shown when on the Open Client Record dialogue.
A client file will always contain a Base Plan, which should reflect your client's current situation as of your most recent meeting. The base plan serves as the foundation for the client's case.
A client file can contain any number of plans/scenarios, which are built from the base plan. There is no limit on the number of scenarios you can build.