Warehouses are where stock is held. An item can carry stock in several of them.
Stock is always "an item in a warehouse"
A stock figure never belongs to an item on its own; always to the item-and-warehouse pair. "12 units" means 12 in one particular warehouse, and the total is a sum rather than a figure anything can be drawn from in one place.
A transfer is two movements
A transfer does not move a figure — it records an outbound movement at the source and an inbound one at the destination. The overall total is unchanged, but both warehouses get their own line in the ledger.
Cost travels with the stock, so a transfer never changes the inventory's value out of thin air.
A warehouse that has been used cannot really be deleted
Deleting is possible only when none of these point at it: a stock level, a stock movement, a cost layer, or a purchase order.
So emptying a warehouse is not enough to delete it — the movements that took the stock out remain in the ledger and block it themselves. That is deliberate: deleting a warehouse would orphan the meaning of every row referring to it.
In practice only a warehouse that was never used can be deleted. One you no longer need should be emptied and left alone; it is not removable.
Access is granted here
You can set which warehouses each user may reach. A user with no restriction recorded sees them all.
The moment you name even one warehouse for a user, they see only those — in the items list, in reports, in reorder suggestions, everywhere. So restricting someone to one warehouse changes the figures across the whole module for them, and that is not a fault.