Which information in supplier defination is Global and which information is Privacy controled

Summary:

Under the same enterprise in the same instance we have many legal entities , many ledgers and many business units and the suppliers defined under this instance may be available to all to use and may be available to specific business unit.

1- In supplier defination Our customer need to know which information is global to all entities in the same instance (means we couldn't control it) and which information we can control its access and give only specific business unit its control.

2-How can we control for a specific business unit supplier information to be viewed in business transactions like create invoices and purchase orders ?