I realise the
OP put forward the no highways thing, but for pure touring pleasure that isn't my criteria. Some highways like the Mt Lindsay are spectacular. I have so many times driven out of beaudesert at dawn and up the hairpins to the border, little clouds about the mountains, hot air balloons taking off on the plains. The place is absolutely spectacular, and the last 15 minutes are 20 kmh hairpins, not a horrible crowded freeway.
The princess from sydney to melbourne can be beautiful also and most of it ain't straight... To me the real appeal is getting off the common routes..