I am posting this to help others with similar issues when switching to nbn.
I experienced the following issues after switching to nbn FTTC. Both issues are now resolved.
1. My houses copper connection was initially connected on the wrong DPU port. In this case you will notice that the nbn FTTC modem's reverse power and WAN will keep blinking with a barely noticeable clicking sound. Before wasting too much time, call up your provider and get them to organise an nbn technician to come around.
2. After switching to nbn, I noticed that the speed of my connection was almost exactly the same as before. But when I connected a laptop directly on the modem the speed increased to the FTTC promised speed tier. Eventually I noticed that the issue was due to a setting in my Netgear Hawk wireless router. I had enabled QoS with auto speed detection and the router had cached a previously detected speed. After running the speed detection again the issue was gone.