Is there anything wrong with always using champagne yeast for meads? I understand it's useful pretty much only if you're expecting high alcohol content, but I'm concerned about off flavors with basic wine yeasts. Any thoughts?
what determines what yeast goes in what beverage anyway?
Let me try to answer both of your questions:
There's nothing wrong with Champagne yeast. You can get it to produce a sweet mead or a dry mead.
What determines what yeast goes in what beverage anyway? Same answer. You use a yeast that produces either a sweet or dry mead.