1. The data sheet for the RealSense R200 camera, obtained from the Vision Accessory Kit information page, lists the depth tracking range as between 0.4 m and 2.8 m.
2. As the Librealsense SDK is used with Aero, a 'Projection' type instruction could be used to determine the depth distance between the camera and an object.
Librealsense has some sample scripts for streaming depth. Full details of the Librealsense samples can be found on the Developer Guide page (linked to below). Go down to the very bottom of the page and then scroll up to the 'SAMPLES' heading to find the information.
This link may also be useful to you regarding the question of working out the distance between camera and object.
Here's the link to the R200 data sheet:
Regarding RealSense cameras with higher specification than the R200: super-powerful new D415 and D435 models that were designd with drones, robotics and autonomous vehicles in mind are on their way. They are not caseless like the Vision Accessory Kit's R200 though, so if it were possible to attach them to a drone then the drone would have to be thought of as being more like a flying robot. These cameras have also not been validated for use with Aero, of course.
1. There is not a definite release date for the D-camera at the moment. They are listed as "coming soon" and then should be available for pre-order on the Intel Click online store. Until then, you can click a 'Notify me' button to be kept up to date with release news about these models.
2. Though they were designed with drones in mind, I do not know what internal testing with drones that they have undergone so far. Suitability for drones was first mentioned in the context of a demonstration of the caseless camera module board, so I would expect that this module will be orderable from Intel Approved Distributor companies such as Mouser and Arrow. The bare board would certainly be the most suitable lightweight form-factor for a drone, rather than attaching the full cased Developer Kit camera.
Here's a video interview from a year ago with an Intel employee that shows the bare module.
There's another video from the same conference that demonstrates depth-tracking a street from a car in motion in real-time using the 400 Series, representing the kind of view that a drone using the camera might have I've set up the link to begin at the relevant part of the video.
3. I would recommend Dronecode PX4 autopilot firmware, which is shipped on Intel's own "Ready To Fly" drone kit.
The Dronecode wiki site has a RealSense installation section.