Although the game is for PS1, i'm assuming that PS2 is faster, and then emulator is even faster than that? However i noticed the top any% hoverless run is very close to any% and is on a japenese copy. Is there an advantage to using a japanese copy?

Japanese loads are fastest.

However, you can only hover for a VERY short time on the NTSC-J version (with an exception). That's why it's not used for regular any%.