It all sounds encouraging, doesn't it!! Good luck with the process. You don't make decisions lightly, so when you do make one, it will be one that will be good for you.The iPhone app lets me change many settings including volume, bass, treble, midrange, and some of the built-in programs like Music, Noise, sound focus, etc. But the fundamental frequency response curve is set by the audiologist.
To do my own programming I will have to buy a bluetooth interface device for my computer in addition the software. And I will need a Windows 10 computer. So I'm not committed to that course of action yet... just investigating.
There is a Hearing Aid forum much like the Nikon Cafe and quite a few members there have reported great success in doing their own programming.