this is currently only possible for extended tracking with the extendedTrackingQualityChanged callback.
The next release of the Native SDK will also include an API for getting the Instant Tracking point cloud.
Will this also be available from the Unity plugin?
Yes this will be available for Unity as well. You can already download the dev-channel release of 7.1 where it is included from our beta category on the download page.
Is there any tracker visualisation that we can enable for debugging.
I'm thinking maybe an on screen interesting points maintained or on screen metrics for probability of a match or somesuch.
That would help us to establish the conditions under which tracking is successfully maintained and when it is lost.