Ah well. I still use Evernote because it syncs well between devices. OneNote syncing is awful. But I have been using OneNote for class presentations because presentation mode is so poor in Evernote and students can't see the notes. Changing the font sizes doesn't help for presentation mode, which seems to be in its own formatted world.
I guess I can just not use presentation mode and show the note raw. At least I can set the font size I want for that.
Now to figure out how to get my class presentations back into Evernote!