I gave up on Harmony Graphics a while back, and instead went with an intelligent display with touchscreen.
http://www.stone-hmi.comWith this one I use a UART port (RS-232), and same protocol for any size screen.
I tend to draw my graphics versus using their design software as my screens are quite simple, I have a set of routines to draw a variety of button grids from array data.
This way I get the display, touchscreen, and bezel all in one.
Paul