The prepareToPlay() methods of the juce::ARAPlaybackRenderer and juce::ARAEditorRenderer classes take ARAPlaybackRenderer::AlwaysNonRealtime as an argument, but the juce::AudioProcessorARAExtension::prepareToPlayForARA() method ignores this argument and defaults to false. It would be usefull to control this argument and set it according to juce::AudioProcessor::isNonRealtime() for example. This can be used to decide which type of juce::AudioFormatReader (Buffering or not) to use, for instance.
P.S. I created a PR:
AudioProcessorARAExtension: Add support for ARAPlaybackRenderer::Alwa… by pierreguillot · Pull Request #1505 · juce-framework/JUCE · GitHub