They aren't exclusive. Something that is easily discovered gives you an efficiency of thought.
But "number of clicks" isn't a measure of efficiency.
What's the time from thought to action? That should be our main concern. If that takes one click, five clicks, ten thousand click, it doesn't matter. Thought to action.
I don’t think discoverable and efficient are mutually exclusive.
Something can be discoverable and still usable in 5 clicks or less (example: most menu bars).