Well, in most parts of the world it's called "6/6" vision. I don't know if "6/6" is used metaphorically in those countries. It is a reference to the familiar Snellen eye chart. 20/40 vision means that, at 20 feet from the chart, the smallest letters you can read are so big that a person with good vision could read them from 40 feet away. Yes, you could use the word "vision" metaphorically and then use "20/20" as a way of saying "perfect." There is actually a stock phrase in English: "20/20 hindsight." This is a reference to the fact that once we know how things turned out, in hindsight we always think we could have predicted them. "I knew politician X would win the election. It was obvious." "That's just 20/20 hindsight. It wasn't obvious at the time."

"20/20 vision" is perfect (or at least very good vision). If you have 20/20 vision, you don't need glasses. The phrase "hindsight is 20/20 vision" is a metaphor. It means that before you make a decision, it isn't always easy to know which choice is best, but after you have made the decision, it is obvious which is the better choice. For example, "This morning, I went over the bridge to get to work and got stuck in traffic for hours. I should have gone through the tunnel instead. Oh well. Hindsight is 20/20 vision." You can use it metaphorically, but as a description of the person's ability - so neither of your examples really work.