You should note here that Forensic auditing is only in relation to fraud, financial claims, illegalities in finance etc etc. So it is fairly specific. Your work could be used as evidence in a court case which is interesting! It is usually also very highly confidential and so you can be in small teams, locked away in audit rooms.
Having experienced general audit, I would recommend you do your grad scheme here first. It will give you an overall view of lots of different businesses just from the perspective of an annual year-end audit process, and then you can transfer/ second over to forensics to check it out! I know a few people that did this route and they found having the base knowledge from core audit really helped, and then they were able to specialise within forensics.
Hope this helps! Good luck.