Connecting a parallel LCD using ST7789 with STM32H743VI
The STM32H732VI has a LCD-TFT peripheral to drive the RGB interface directly, but if you don't want to use it, you better use the Flexible Memory Controller (FMC) peripheral to map the LCD display into memory bus, so DMA can be used with it. Connecting it to simple GPIOs can't really use DMA, or at least it would be awkward to use DMA to toggle GPIOs to get memory reads/writes to the LCD.

1) The FMC pins must be used - just any GPIOs will not do.

2) The DMA controller can do memory-to-memory DMA block transfers. I don't see how the timer would be used for DMA transfers in this case.

3) Maybe Chrom-Art is worth using, if you need operations that it can perform, but the usefullness to directly use it over FMC to drive external framebuffer can be limited. At least you can use it on internal framebuffer that you can then copy to your display, if the Chrom-Art output is not directly compatible.