There are additional online Q Banks associated with all of the Manhattan Prep books, yes, but I would consider those secondary for Quant and Verbal. The main assignments / problems will come from either the Manhattan Prep books or the Official Guide. I'd do those problems first before going into the additional Q Banks. (This does not apply to Integrated Reasoning—there, you will use the online Q Banks as part of your main assignments, since several of the IR question types are interactive / have to be delivered online.)
I'm not sure whether you're already registered for a class? If so, I would also ask your instructor for advice about how best to use all of your resources. They can give you advice that takes into account your strengths/weaknesses and your goal score.