I saw the final three episodes last night (one on my PVR recording and two on 7plus). I agree with JBar that Tarryn was robbed. She was arguably the best performer from the grand final and the only contestant to get the perfect 100, and deservedly to be in the final three. Royston stumbled during his first performance in the grand final, but somehow got 91 (maybe there were few sympathy votes from the judges?), while Lai just survived the tie breaking vote.
I did a Google search after the grand final and found out Tarryn sang the theme of Home and Away in 2009 with Luke Dolahenty. No wonder her vocals are so good. She is also a member of Hillsong Church singers. And Tarryn and Royston came from David Jaanz music academy which nurtured many other singers.
As for the other grand finalists, Teagan the wildcard has secured a year long contract from Royal Caribbean International and will perform on its brand new Spectrum of the Seas around the world during 2019.