I did "the lap" in 1982 so my experience is pretty dated, though I have been touring extensively since. I did it on a 27" wheel touring bike with 1-1/4 in tyres as that was all there was in those days. There were some stretches of unsealed roads even on Hwy 1. Would have been easier on a fat tyre bike.
Starting from Perth, it would be good to spend some time in the south west of West Australia. That has the best scenery of the state: tall forests, wineries, coast. From there you're on the Nullabor which is a good introduction to outback cycling. Some people find it dull, but I love desert riding. Takes a while to get into, but forget about gormet dining and encounters with locals. Just enjoy the moods of the desert and bike pace is a good speed to get into it. It's much more mind numbing by car or bus.
Once into South Australia and the East Coast, you'll have more options for routes off of the main highways, and a lot will be sealed so your bike should be fine, especially if you don't mind the occasional dirt road. The further north you are though, the options again become limited. There are shoulders on the highways in places, but not the whole length. Local knowledge might help for alternatives.
Once you leave the East Coast to head inland, you're into outback cycling in a big way. Carry your own supplies and water. Camp by the side of the road. It's a great freedom to be able to pitch a tent just about anywhere at the end of your day's ride.
For food, if you visit wine regions, there are sure to be good places to eat. Elsewhere, it can be hit and miss, so you're best to carry your own. Stock up in the bigger towns for more exotic supplies as all you get is tinned food in the small towns and little in the way of fresh food. You could also package up food and send it down the road via bus freight or plane old Australia Post. It wouldn't cost much.
I'd imagine the majority of encounters with people should be fine. When I did it, there was some other cyclist who had a less than favourable experience with a cop in Port Augusta, but that would have been an isolated incident.
World cyclists Tim and Cindie downtheroad.orgdowntheroad.orgOpen ↗ have been in Melbourne recently and commented that they thought that Australians were amongst the most friendly people they have encountered yet.