What is 2-way, 3-way, 4-way matching? How is this set-up?

2-way matching verifies that Purchase order and invoice information match within your tolerances as follows: 
Quantity billed <= Quantity Ordered 
Invoice price <= Purchase order price 
(<= sign is used because of tolerances) 

3-way matching verifies that the receipt and invoice information match with the quantity tolerances defined: 
Quantity billed <= Quantity received 

4-way matching verifies that acceptance documents and invoice information match within the quantity tolerances defined: 
Quantity billed <= Quantity accepted. 
(Acceptance is done at the time of Inspecting goods). 

Whether a PO shipment has 2-way, 3-way or 4-way matching can be setup in the Shipment Details zone of the Enter PO form (character) 
Receipt required Inspection required Matching 
YesYes4-way 
YesNo 3-way 
No No 2-way 

What are the documents not supported in PBWC?

Following document types are not supported in PBWC : 
Planned PO 
Local Blanket Agreement 
Local Contract Agreement 
Scheduled Releases 
BPA Releases 
Quotations 
RFQs 

Are Preferences supported in PBWC?

Preferences are not supported in PBWC