FYI. I tried using the ASIair Pro with my Evolution 8" SCT and had mixed results. I went to ZWO support forum and found that it can connect via handcontroller and that it has to be at 9000 Baud. My handcontroller is old and has a telephone jack/port for connection. I ended up using my Starsense handcontroller to connect because it has a Mini USB port for connection. Anyhow, at one moment, the Alt-Az mount went haywire and slewed up to zenith and beyond. I tried to get platesolving to work, however, it kept failing and I gave up... Ultimately, I got the sense that it can connect to the mount but with snickers/jeers/whining.
I can see how it would be best to pair the ASIair with a EQ mount.
So you went with the ASIAir Pro after all. I wonder if some of the problems you experienced might have to do with using the StarSense HC, and whether getting a telephone jack/port to USB cable for the Nexstar HC might be the answer?
As I mentioned I did get a plate solve the other night, and at ƒ10 at that. I have no idea what it solved, but it did report success, and told me my focal length was 1730 mm, rather than the 6SE's nominal 1500. This may have been due to the camera being inserted in the diagonal, I really don't know, but the 'Pro seemed to think all was well.
I also seem to have got it to do GoTo's and centring. I did a fake indoor alignment on Venus a few minutes ago, then told the HC to go to Jupiter, and took note of the Axes positions. I then told the HC to go to Saturn. Once there, I told the 'Pro to go Venus, which it did, and then to Jupiter. The Axes positions were virtually the same, and while I was checking that, the scope made some small movements, and a red error message appeared in the ASIAir app, something along the lines that it had failed to centre the target and was trying again. It again failed of course, as there were no stars to plate solve, and attempted another try before I cancelled the operation.
The mount didn't go haywire fortunately, but from what I've read here on CN, Celestron mounts sometimes do that -- no idea if it might be connected to the 'Pro or not.