There are subtle differences in the regional ROMs regarding character voices.
One of the N64’s biggest flaws was its 4KB texture cache. The "Better" hack rewrites the microcode to allow for higher resolution mipmaps. In practice: mario kart 64 u z64 better
It uses "Big Endian" byte order, which is the native format the original N64 hardware uses to read data. There are subtle differences in the regional ROMs