Regarding the nextion display, unfortunately, while in general, idea is good, there are several key disadvantages:
1. High cost
2. Bad quality, low contrast, bad viewing angle and not sunlight readable display.
3. Need for SD card
4. Long boot time
5. Complicated, badly written and not user oriented IDE

So nextion is junk, and unless they fixed all these 5 (which is not going to happen anyways), I'm not going to look for it

Contrary to that, ST7920 display is pin to pin compatible with standard 1602 LCD modules, has actually two display framebuffers - one for HD44780 mode, another for graphical, and it does OR for them automatically - so you can write text via HD44780 mode, and use graphic mode to only display graphical elements, their overlay is automatically handled by display - thus removing requirement for large amount of ram, rom, eeprom and need to keep separate framebuffer.



As I understand, working with HD44780 means manipulation with Enable and RS pins, and setting data pins according to required bytes to be sent, and spitting them into two 4 bit parts. So since I usually connect 44780 pins to single port in sequence - like data lines to portb.0-portb.3 and RS and E pins to PORTB.4 and PORTB.5, I guess there should be a statement, which allows to set port bits according to certain variable bits. So after reading HD44780 manual, I don't think it will be too complicated to do bitbanging and drive it in that way...