Hi,
You need to define a order type for SO and BO in IMG and use a seperate infoobject if necessary (This will helps you only differentiation the order type and can be used only at reporting level), But all these you would have done at initial design and implementation stage. doing this at the middle of your project will lead to complete alteration.
Loading SO in SPP is just to support forecasting services to derive forecast values.
DRP - Calculates the demand based on your Forecast values and inventory levels and not specific to SO or BO,
BO will comes into play, when an already initiated procurement order (Release --> SA/PO) has some quantities which are not received on the determined time will show as overdue/BO.
May be when you're integrating with CRM, BO will be identified automatically.
Thanks
Vinoth