Under Oklahoma law, a 15 year old having sex with a 14 year old is not a rape. The perpetrator must be over the age of 18. Unless the rape is forceable. Then age doesn't matter. But if the act is consentual, then there is no statutory rape if the perp is under 18. So 2 high school kids having sex is not rape under Oklahoma law. As far as lewd molestation, then the perp must be at least 3 years older than the victim, and the victim must be under the age of 16. So, in your first hypothetical, there is no lewd molestation since the kids aren't 3 years apart. So a 19 year old having consentual sex with a 16 year old is not a crime either. A 17 year old having sex with a 15 year old is not a crime either.
As to the peeping through a hole in the locker room, as long as the age difference is less than 3 years, or the victim is over 16, there is no molestation. And the exhibitionist example, as long as the kids are over 16, no crime. If the kids are under 16, and the perp is over 3 years older, then it is a crime. But not one I believe is ennumerated in the death penalty statute.
What's the age of consent in Ok? If it's 16, then anyone who has sex with a minor is guilty of a sex offense of one sort or another