1. Don’t use a partner orchestration port here. Instead, select “Routing will be determined by filter expressions.” Then you could creat a property schema with a context property named Vendor, and set the value of the context property before sending the message to the port. Then you can create a send port for each vendor (assuming there are not too many) and configure a filter expression on each send port. For example, you could have one send port with filter: Vendor = ‘VendorX’, and another send port with filter: Vendor = ‘VendorY’.
2. It depends. If you have a very small number of vendors ( maybe around 5 or less), then direct binding would be a good choice because you only have to create a few send ports. If you have many vendors, then dynamic binding is a better choice because you can use a single send port for all of them.
You do have another option: role links. Role links can get cumbersome though, so you would probably be happier with direct binding or dynamic send ports.