You can use any region (if you use PAL, there's a different category for it)

However, keep in mind that JPN is faster due to text and other differences, so you may want to switch to JPN once you're used to the game :)

(If I got anything wrong, feel free to correct me, I don't speedrun this game yet)

there is a couple of tricks exclusive to the JPN version which makes it faster to run, however you can still run the US (NA) version of the game as well, which is what I do.

Use JPN if you have it readily available, other wise It can be a little bit of money to ship it in for what is only a 20-40 second time save in any% No OoB.