I only did the magnetic calibration it always wants you to do the first time you fly, and sometimes randomly if there's interference. It seemed to go a lot smoother than with my Phantom but maybe because I've done it a few times now?
This has always been my experience with RTH though I never had the precision landing thing, usually it's close enough that it's not a problem, I never use it in dense areas
Maybe if we ever get that Phantom RTK drone it can get us within a foot
I have an iPhone 8 Plus, looks like the mavmount or similar is the only choice. I really don't like the mavic controller design very much compared to the Phantom