For true AB biasing on bipolar amplifiers the bias supply must have a low source impedance able to deliver as much current as the devices been biased need at maximum drive level,
for instance if your transistor is operating @10db gain & full ouput pulls 10amp of collector current from your psu the bias supply should be able to provide 1amp or more without folding back the bias voltage,
the only way I know of doing that with good regulation is using an actively regulated bias supply,
just like the circuit in your linear type psu but setup for low voltage,
The other methods even when using a regulated supply for the bias divider & clamping diode vary the bias voltage with drive level even though the bias supply from the regulator is stable,
the worst of all are the simple unregulated supply feeding a divider like Texas star or xforce,
active regulated bias supplys allow a lower idle current while still remaining in class at all drive levels,
Bipolar output transistors and bias switching transistors conduct harder the hotter they get causing idle current to go up with increased temperature,
a good bias circuit not only keeps bias voltage stable under all drive levels it compensates for the increased conduction with temperature by reducing the bias voltage proportional to temperature keeping the output devices much closer to the correct idle current.