Get a local sim its way cheaper in OZ than it is here.

I found Belong to be the best value and they did not give me an ID check and uses Telstra's 5G network (Capped at 100mbps)

Optus was VERY bad their systems were hacked recently and they dont give you 5G for free (Which actually came in handy) and wont sell it to you without a fight for some reason even when i said i want 5G. 

Scenario where 4G actually was un-usable was in Gold Coast and it appears their 4g tower was overloaded and was getting between 0.5mbps-3mbps with a 800ms ping.

Meanwhile 5G on Telstra was going at 200mbps everyone i know in OZ has said Optus is no good and i can see why.