NTSC and PAL are not definitions of the HDMI Standard. But HDMI can use various frame rates.
PAL is 25 frames per second (or multiple). NTSC is 24 or 30 frames per second (or multiples).
A good HDMI to Video converter will be able to select between those (I use an Atomos Converter/Scaler).
If your converter selects the output-standard from the HDMI frame rate then you may try to set it in
/root/ETC_MOTHER/main.py:
#draw the main screen, limit fps 30
clocker.tick(30)
hwscreen.blit(screen, (0,0)
It is quite at the end of the file.
The aspect ratio is defined in etc_system.py:
RES = (1280,720)
It is in the first 25 lines…
But keep in mind, that all the modes use hardcoded width and height values. If you want a mode to adopt the corresponding screen dimensions you have to use screen.get_width(). You will have to change each and every mode on many places within the mode. I’ve done that and it is … hmmm … exhausting 