No, store_slice and store_ref are two different functions with different inputs and outputs.

store_slice adds slice bits and slice refs to a builder, while store_ref adds a cell to a builder's refs. Using store_slice with load_ref and begin_parse is not possible.

Regarding the most efficient way to store a slice as a ref, there is no one-size-fits-all solution. One possible method is to use builder.store_ref(begin_cell().store_slice(slice).end_cell()), but this may involve creating an extra cell.

The most efficient way to store a slice as a ref will depend on the specific requirements and constraints of the application, and may involve trade-offs between gas cost and complexity of the implementation.