The number of Fulfillment Orders that would be created for this order is one per destination, totaling 3. A Fulfillment Order is a record that represents a group of products in an order that are fulfilled together from the same location. A Fulfillment Order has a lookup relationship to the Order Summary object, and it contains information such as the fulfillment location, delivery method, status, etc. The number of Fulfillment Orders created depends on three factors: Fulfillment Location, Delivery Method and Recipient Address. These factors determine how the Order Items are grouped and allocated to Fulfillment Orders based on routing rules and inventory availability. In this case, since the products must be shippedto three different locations, three Fulfillment Orders are created for each destination. Verified References:https://help.salesforce.com/s
/articleView?id=sf.order_management_fulfillment_order.htm&type=5

Two reasons an admin should choose an Event over a Trigger when it comes to building out a solution are:
Events are asynchronous. This means that events are processed in the background, without blocking the main execution thread. This can improve the performance and user experience of the solution, as well as avoid governor limits and timeouts.
Events do not participate in a transaction scope. This means that events are independent of the transaction that publishes them, and they do not affect the rollback or commit behavior of the transaction. This can avoid unwanted side effects and errors in the solution, as well as decouple the logic from the data.
Verified References: https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta/platform_events
/platform_events_intro.htm https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta
/platform_events/platform_events_considerations.htm