Hi Alex,
Delta Transfer means whatever objects are present in the existing Integration Model and if any changes were made in those objects then CIF will transfer only those changes. (CFM1/CFM3).
Report RIMODINI is special report provided by SAP which will force in all the changes for all objects. So basically its like full load of all the objects present in Integration Model and is equivalent to Initial Load.
No RIMODINI is not needed to be executed after every CIF.
Regards,
Alok