Three month ago I upgrade sony a5000 to a6600. Before I have use sony a5000 about 6 years.
But I still use ergonomics a6600 as a big a5000 with ibis end evf. Still don't customise all custom buttons, don't realize quick meny idea, custom modes end etc..
Most time I do photo, A-mode, sometime S-mode. Shoot JPEG.
Lenses:Zoom 16-70, 20f2.8. (also have old vintage soviet lens, but practically don't use it).
Now I only customise C1 for DRO\HDR option, and C2 for manual focus magnification.
So, I will glad if APSC sony community members share experience about a6600\6400 usage and ergonomics customization mostly for photo.