You can create a plugin for after Place order action in Magento 2 using afterPlace() plugin method.
When you required to check or get data after place order in Magento 2 or save data to other tables after place order successfully You can use afterPlace plugin from OrderManagementInterface interface’s place() method.
place() method from the Magento\Sales\Api\OrderManagementInterface interface class used to Place order operation in Magento 2 from checkout page.