Hi, some categories needs a race file as base for the run. I'm pretty sure you can't import one on Switch. How is it handled there? Can I prepare a file myself? Is it enough to got Deku Mask and Song of Healing or is there more to pay attention for like a certain rupee count?

You are allowed to make your own race file.

Here's everything that's required for one: https://www.speedrun.com/mmextras/thread/0yb49

We don't specify how much magic you must have at the start, though if you want a full meter shoot skull kid first with a bubble, then break one of the green pots and fill your meter.