After the first two kilometers you can either go through Höllentalklamm or take the Stangensteig. If you haven't seen Höllentalklamm yet, I recommend to go there.
The via ferrata to Grießkarscharte is really beatiful and has a steel cable from the beginning to the end.
When there are a lot of people that are ascending Alpspitz ferrata you should choose either Schongänge or Nordwandsteig to descent from the summit. These via ferrata's both start at the end of Ostgrat.
When you are tired or run out of time you can use a cable car down (Kreuzspitzbahn or Alpspitzbahn).