> They are the same system device but they are separate devices to Mixxx.
 
Is there an Indicator, to detect your case? Or do we need a preference option? 

> This change adds a 1.5x latency delay to my microphone unnecessarily

Actually only one additional latency. 

> The current master works perfectly 

Are you really sure, there is no jitter or overtake?  I ask, because in current master the underflow counter is not incremented in such conditions. 

> In the settled state it should not be gaining or losing frames. How does it slowly move to one chunk available in that case?

In this case (it happens always after start) it looses or add one frame per buffer. This is much better than loosing a whole frame in case of a jitter.