Emailed my Aussie daughter for you. She lives in Melbourne and hired a motorhome a couple of years ago.
Here is her reply.
There are literally hundreds of campsites along these coasts both commercial and bushland (I believe those might be the 'wild' campsites ðŸ˜€)...the scenery along these routes is absolutely breathtaking - sssh...don't tell everyone! The fresh produce especially fish/seafood will be some of the best you'll find in the world. The crayfish in South Australia (Robe or Beachport) is a must...purchase straight from the factory door.
Plenty of MH hire companies...Apollo is one of the biggest & you see many of them. Website has info on some campsites etc