assuming you're referring to the setting in View > Options... > MIDI > Playback > Queue timer (resolution)
the best would be set to "HR timer", always... but this mostly only deals with audio and MIDI sync in regard to external (to qtractor) clients or devices.
ALL internal processing (within qtractor premises that is), plugins and looping included, is frame/sample accurate; automation being the exception as it runs on a fixed 64frames resolution (or even less, if the period buffer-size is insanely shorter than that).
but this is all moot or of no consequence if and when the system is loaded or already hosed--there's always a physical limit when scheduling threads start falling short to their deadlines--there is always a limit to what any physical entity can do, no matter what you may call it "real-time" or else...
assuming you're referring to the setting in View > Options... > MIDI > Playback > Queue timer (resolution)
the best would be set to "HR timer", always... but this mostly only deals with audio and MIDI sync in regard to external (to qtractor) clients or devices.
ALL internal processing (within qtractor premises that is), plugins and looping included, is frame/sample accurate; automation being the exception as it runs on a fixed 64frames resolution (or even less, if the period buffer-size is insanely shorter than that).
but this is all moot or of no consequence if and when the system is loaded or already hosed--there's always a physical limit when scheduling threads start falling short to their deadlines--there is always a limit to what any physical entity can do, no matter what you may call it "real-time" or else...
cheers