I don't think there is much connection. If anything I get the impression extremely good looking people are a bit less likely to be nice. Probably a combination of not having to be and having to deal with other people's reaction to them all the time.
I'd say only about one person in maybe 50 is very good looking (after they are an adult) and maybe one person in 20 is very nice so a person being both is one in a thousand.
Beauty is in the eyes of the beholder and in the mind of the one being seen.
Remember that all the surface stuff is temporary, it will fade in time. But the stuff inside, the real nitty-gritty that makes up a real person (and not the best side they want to show you) is where intimacy truly lies.
I don't know if inner beauty and outer beauty somewhat correlate but I only rarely met people, who have both.
Both have nothing do with each other. The girl I like was pretty much unattractive to me when I first met her. As I got to know her more, I began to fall for her. Then same person became very attractive to me.