You can make the display slightly faster. It uses software SPI. For Marlin 1.1.x, the timing values are defined in Conditionals_LCD.h
// #define ST7920_DELAY_1 DELAY_NS(125) // #define ST7920_DELAY_2 DELAY_NS(125) // #define ST7920_DELAY_3 DELAY_NS(125)
The lion kingdom managed to get them down to 64, but no lower.
More SPI delays are defined in ultralcd_st7920_u8glib_rrd.h
ST7920_WRITE_BYTE, ST7920_WRITE_BYTES, ST7920_SET_CMD, ST7920_SET_DAT, ST7920_CS
all have delays but the lion kingdom didn't have any luck reducing those.