As long as you are aware of the risks, the best judge is you. There arent any laws around being in a non-sexual relationship where one person is under 18 and the other over. Once you turn 16 its not illegal for someone to have sex with you no matter how old they are.

Is it wrong for a 20 year old to date a 16 year old?

No, its not against the law for a 20 year old to DATE a 16 year old. The definition of date means to go out together to a movie or to dinner or dance. It does not mean having sex