do I have to specify which region the game is running on or can I just pick none? cuz' I don't what the correct option is. asking for if I decide to do a speedrun.

You can tell by the region just by the intro screen. If it's in japanese then it's the JPN Region, if it's in English then NTSC/EUR region (doesn't matter).

I personally like regions because there is gonna be a point in time with this game where version and region could impact the speedrun - so knowing that information is good upfront.