Replace a data table with another and keep visuals and in query measures

If you go into transform data, click the current table you can swap the M code in the advanced editor. Provided columns are the same visuals should maintain.

Dataset size refers to the size after it is in vertipac which has amazing compression. The whole thing however is loaded into memory at that point so the bigger it is the more resource it uses. If you're using a star schema power bi can handle vast data sets. Have a read of Data reduction techniques for Import modeling - Power BI | Microsoft Docs