Available for all integrations.
The main thing to consider when considering Source v Destination is that the Source store can trigger inventory updates to the Destination Store on both manual adjustments and orders. A Destination store only triggers adjustments through its orders, such as when an order is created, or cancelled or refunded with Restock checked.
Syncio is designed this way as the Source store is the store that holds the master inventory and is the store that fulfills and ships the order to the customer.
The Destination store is the store that syncs product from the Source store to list and sell. With the Orders Add-on (Shopify only), orders can then be pushed to the Source store to drop ship to the customer.