Partition switching vs schema transfer
Do you have any advice or suggestion?

All the operations you described are metadata-only, so I wouldn't expect any significant difference in performance.
It is strange that you don't have Foreign Keys on your [App] schema.  You've already paid the cost of checking the DRI, and if you have validated foreign keys in your database the Query Optimizer can take advantage of them.
Schema transfer would allow you to leave all the foreign keys in-place.