I heard tight clothes in the minor awrah doesn’t actually fulfill the requirement of covering is this true? Also is it permissible to look at the awrah of someone under puberty?

There is no need to look at the awrah for someone who is under the age of puberty, unless there is a need, like changing a diaper, for example. As for the minor's awrah, I don't understand; do you mean that it is a little bit tight on the belly or so? If that is the case, then inshallah tabarak wa ta'ala it is fine. However, it is not something that the people of muru'ah (those of honor, status, and respect) would do—to wear tight clothes on their thighs, near the knees, or on their bellies and so on. No, wear something that the people of honor and respect normally wear.