Just took a look in the rules for all of the major categories. The rules do not mention whether emulator usage is allowed or not at all. The only mention that I COULD find was on the "Submit run" screen (It's under the "Platform" drop down menu.

In my opinion, you can play on emulator IF, AND, ONLY IF, you are merely practicing runs.

I would highly recommend buying a Nintendo Switch and a digital copy of Breath of the Wild if you want to submit runs.

I hope this helps

it says in the "Submit Run" menu