I think people who like ideas like polyamory have misconstrued notions about what monogamy is, which is a general cultural problem in western societies these days.
I don't own my partner and she doesn't own me. I give myself freely to her and she does the same. It's not about expectation, but commitment. I promise her she's the only one for me, despite my very human desires, and she promises me the same thing. This is healthier than the pervasive "ownership" mental model, because we both very much are aware that we have human and animal desire, and understand that the commitment is freely given. We don't get mad at each other for being attracted to other people, and feel no jealousy, we would feel betrayed if the other broke the commitment, because we were promised something by the other.
The idea that monogamy is the default in relationships outside of marriage is a very new thing in US culture. There was a time, not so long ago, when the point at which monogamy began was marriage, or for some, engagement. Needing to define being single in over convoluted terms like "polyamory" is a bit ridiculous.
I've always been very casual about these things with partners. Some can't handle it, they're jealous by nature or something. Usually, being clear "we aren't committed until we talk about that and commit" is a pretty easy to digest thing for people, even if they default to the opposite usually.
On a less personal note, it's no coincidence I think that the most successful cultures in the world were and are monogamous by social expectation. Polyamorous social structures are not conducive to responsibility with regard to rearing children, and are more often than not to leave women in a difficult position. As such, women expect commitment from men where there are few options to prevent pregnancy. That's not to say anything about the spread of disease. Jealousy is still a problem, and leads to conflict. Polygamous social structures, the second most successful of the reproduction/sex oriented social structures, lead to swathes of unmarried men, and you get rejections from the tribe, hostile takeovers, warlike cultures designed to dispose of the men who will not hope to reproduce. Monogamy is the stable arrangement and it shows. Other more exotic complex social arrangements tend to be very niche, small tribal groups relegated to basically Africa, and don't scale well.
I think if young people want to have fun, do it, be clear, if someone doesn't like it that's their decision to not participate. But slapping labels on it like it's some revolution in sexual dynamics is silly. Be prepared to outgrow your exploration, read the allegory of Chesterton's fence to understand why.