Ok first of all there is no "class AB1 or AB2" biasing for a bipolar, solid state amplifier. AB-1 and AB-2 are used to describe the element of a *tube* that is biased with respect to another element in a tube.
When referring to a solid state amplifier, there are of course, different classes of amplifiers. Class "A" for an RF amplifier for all practical purposes would be overkill for most applications. There are several reasons for this. The first, is that the amplifier would generate a lot of heat. The second would be that careful design techniques would have to be implemented to prevent oscillation. The third, is that the amplifier would only reproduce the signal's waveform that is fed into it. (not the same as the popular "garbage in garbage out theory that circulates on here all too often) Meaning that is a radio or exciter would drive the amplifier with an AB stage, then an AB stage for the final output, or amplifier would be sufficient.
Class AB would be the best trade-off for linearity and efficiency. In reality, a properly designed class B amplifier would work just fine if it had push pull stages. Even the worst of the CB amplifiers on the market, and don't get me wrong, there are some pretty bad ones out there that people call class "C" aren't really class C by definition due to the fact that they don't have any negative biasing but rather just have no forward biasing and therefore while for all practical purposes are class C, they do not operate "deep" into the class C region. I still disagree with them being used for AM or SSB modes.
Ok that's it for amplifiers.
With respect to audio fidelity, there are several issues at hand. The first is the audio cain inside the radio leading up to the balanced modulator. Typically the audio has a high end rolloff, and a low end rolloff sometimes too soon. By changing capacitors in this section one can tailor the TX audio accordingly. In addition some filters can be widened a bit as well. However this does no good if the RX end is very narrow.
At any rate, just some things to think about.