You can fly up to 150kg MTOW with a Remote Pilot Licence (RePL) over your own property as long it is not for reward, anything over 150kg requires an experimental certificate and needs to be registered with CASA.
You can fly up to 25kg MTOW over your own land with no training or licence required
A 150kg mtow drone is huge, the T100 is 3.2m prop tip to tip and 1.8m with the props folded.
That said there are lots of operators using drones without any regards for licencing, registration or the regulations. It's a huge problem in the industry