Hi @Pradeep-Jaiswal ,
I think you meant to use custom schema and then map standard AA XDM fields to custom XDM fields in data prep as dataset is automatically created in Analytics Source Connector. I think this the best possible option as the transformation needs to happen at some point to align the different sources and having it done at source makes downstream processes easy and removes the need of repeated transformations every time you need to use this data.
Cheers!