Optimized load is where you pull data from a qvd without any transformation or where clause in it.(basically data processing). Aliasing is an exceptional to this.
So if you want it to be optimized push the calculations to the place where you are creating the QVD files, should be your exctract. But to have it handles at extract or a different transform layer should be decided with the dandwidth you have between Qlikview and DB. and the DB should support the transform Queries.