Since you are in Australia, you probably have a 'warm' climate.
The engine's tune is aggressive. When using the lower octane fuel, you are probably giving the knock sensor a workout. I've noticed this with my Camry 2.4l. Run great on econo-fuel all winter long. As soon as it warms up, have to step up to mid grade. You don't need the book to tell you what to do.
Don't confuse 'cam timing' with ignition spark timing.
In the old days, we would install a cam straight up and hope for the best. Since manufacturing clearances were imperfect, we then could install the cam with a slotted/keyed pulley/gear and adjust it either retarded or advanced, to make sure it was accurately 'straight up'.
And, some adjusted it for power. You could install the cam, then either retard/advance it for more torque down low or more HP higher up in the rpm band. We couldn't have both. VVTi adjusts that 'slot' on the fly using oil pressure and gives us both.
The amount of cam phase is growing. Earlier systems were only several degrees and hit or miss(fixed point). Eventually we will see accurate 'electronic' servo control with major angle cam adjusting, along with broader 'variables' tuned for the rpm/throttle position.
The 2azfe's VVTi is intake cam only with 40 degrees of cam adjustment(that's a big slot), ECU controlled by using oil pressure.
Some automakers eliminated EGR by adjusting the exhaust cam for reversion in place of controlling the EGR valve. So, we have engines with either intake cam adjustment, exhaust cam adjustment, or both. Adjusting the cams will make more power everywhere and improve emissions.
If your power loss is noticeable with temperature, you should inspect your cooling system. Make sure radiator has nothing blocking it. Test the thermostat and make sure e-fans are cycling as required. You could also do some 'cooling' mods like bypassing the TB coolant, installing a cold air intake, a bigger radiator, or insulate wrapping the exhaust. Also vary the gas stations to rule out low quality gas.