if your tables are loaded incrementally in the Ingest, the automatic setting will automatically load incrementally from Ingest to Prepare. You don't need to set up incremental load explicitly. You do need to do that from one Data Area to another.
There are some slight complexities in the area of deletion handling depending on what you want to happen and how you want to be able to see that in Prepare. In general, I avoid turning those on in Ingest if I don't need them as they require pulling the whole PK set from source.
You do not need to change the table to incremental load, Automatic is enough if the source table is running with incremental load. You need to check that the mapped table has the I icon to see that it is being incrementally loaded.