Hi, Here’s how they work: 1. If I had a choice, I’d rather I never knew you. → Awkward. Better: “I’d rather I had never known you.” 2. If I had a choice, I’d rather we never met. → OK, casual and understandable. 3. If I could go back, I’d rather we never met. → Good and natural. So #2 and #3 are fine. #1 needs revision.

They're all fine sentences! If you want to make them more grammatically correct you could change them to "I'd rather we'd never met" or "I'd rather I'd never met you" but they're 100% understandable as they are.

Are these sentences OK? All sound good, but some speakers may have a preference.