I found the answer.
This field is really related to the Data Query Associated Data Template.
When you link a XML to a host, your should link it in the "New Graphs". So, what we see in the "Output Type ID" field in Data Source tab is the result from this link.
As you wisely pointed, we can use the same internal data source names for different XML scripts and link the same graph templates to different XML scripts also, without any damages to Cacti funcionality.
So, the only solution I found to graph old Data Sources, using another XML script with the same query structure is create new graphs linked to the new script (that uses the same internal data source structure, so I can use old RRDs files without any change) and change the Data Source path created to de old one.
Even it's a laborious work, at least, we have a solution.
Thanks, your appointments were definitely helpful to clear this path for me.