https://www.speedrun.com/Speedrunning/forum is a better place to ask your question since your problem is related to hardware for speedrunning a specific game (and some other stuff). However, I'll still indulge an answer.

Your best bet is ask the community directly about your situation, as this is a specific game and I don't own a Mario Kart game. According to their current rules, you cannot use emulators. However, there seems to be an ongoing switch to in-game time which may allow it, but there's no solid date when this will happen and discussion of allowing emulators will be conducted after the switch. Link to their forums with all the information you could ever ask for: https://www.speedrun.com/mkw/forum