> My understanding is that scholars also believe that Siddhartha Gautama, the historical Buddha, was indeed historical, but the contemporary sources are weaker.
This is correct and as for which parts of the text are original, philologists such as KR Norman, Gombrich, Vetter and Bronkhorst have come to some consensus (like on the four noble truths and dhyana), excluded some things and some things are still debated.
This is correct and as for which parts of the text are original, philologists such as KR Norman, Gombrich, Vetter and Bronkhorst have come to some consensus (like on the four noble truths and dhyana), excluded some things and some things are still debated.