Demand Schedule to ASCP plan

Could you please clarify what is the major difference between Addition of Plan and FCST as demand schedules to plan.

Ex: Plan A , Plan B

Plan A - Inter org demand needs to be passed as demand to Plan B

Plan B does not have Plan A orgs

we have two options to send demand to Plan B

Option1 )  We attached Plan A as demand schedule to Plan B

Option2) Extract the data from Plan A (msc_supplies.source_organization_id=Plan B organization), and order_type=5 (Planned Orders)

create a designator and place this extracted data under this.

Attached this Designator to Plan B