I've had really good results by blending fresh peaches (or peaches that were fresh frozen) with apple juice in my blender, then filling my fermenter with that. I use between 1 and 1.5 lbs of Peaches per gallon of intended end product. I don't see any reason to add additional sugar or canning syrup. Starting gravity is typically around 1.060, which will result in around 7.5% alcohol if fermented to full dryness. That is perfect, unless you are trying to make something more wine-like.
I believe that by fermenting on the actual blended fruit, I extract much more of the peach essence. The downfall of this is that I have to do 2 additional rackings compared to a typical cider batch in order to get rid of sediment and end up with a crystal-clear end product. 1st racking to get the liquid off of all the ground up fruit occurs after the initial fermentation period, once gravity has dropped to 1.010 or less. At that point I add more apple juice due to the volume loss from the fruit and allow fermentation to continue until complete. Rack again for final clearing, with a potential additional racking during this phase if needed, depending on how clarity is proceeding.