Generally, all Seas really does is lower the cut off a little or prioritise you over others if you fall into the middle band. Some universities like Melbourne uni devised schemes to take this into account ie. Access Melbourne which guarantee you a place with a lower atar than is normally needed. Eg. Bach of biomed 2011 clearly in was 99, however with seas, you only need 95 above. Other unis like vic uni simply prioritise you in the offer selections if you fall into the middle band.
However, in order to answer your question fully, may I ask what kind of fields/courses you are looking at?
Do share as you're not all alone. I'm sure lots of other people are just as confused during these times and AN will definitely be able to give you lots of plan Bs, Cs and Ds if plan A doesn't work out.
All the best! ^_^