So I was thinking of running this game but I don't have a Wii U Can I use an emulator?

You can if you want I guess, however there are not many categories that are offline that are available with an emu, because as far as i know cemu doesnt have online support, but yeah you can

Cemu speedruns o_O

I'm thinking of just not allowing it for top runs, because of weird load times, i dont see any reason not to allow it at all though

Create a separate leaderboard for emus is better I think.

Why not just buy a Wii U like everyone else? Not everything is free.