Yes, I think you’re right. I was idly looking at the settings page thinking about what it could look like, and I think one per setting would be too much. You’d want the best ‘short’ description next to the setting no matter what, and I can’t picture how to put anything extra in that wouldn’t detract from that simplicity.
But a quick reference would be good. Are you thinking inbuilt, or a link to some kind of FAQs set-up here on Meta?