The defining characteristic for which "type" of relationship style you are most suited for seems to boil down to one trait (with two applications). So I would focus less on which relationship type you fall into and more on your personal approach to relating with your partner.
1. Authority and Responsibility: do you believe that you have authority over and responsibility for your own time/feelings/body? Do you believe that your partner has any "duties" related to tending to your emotional state? Do you expect that they should maintain partial ownership of you?
2. Authority and Responsibility: do you believe that you have any authority or responsibility over your partners time/feelings/body? Do you have any say in what they do with their time/emotions/body? Do you expect to maintain partial ownership of them?
In the end, this is the building block of how you are going to relate to your partners. This is the one trait that keeps popping up on these boards and in the relationships around me, and in my own previous relationships.
If, like me, you claim total ownership of your own time/feelings/body and claim no ownership of your partners time/feelings/body then you are polyamorous by default. More precisely you would fall into a relationship anarchist or independent poly type.
At the far other end where a person claims a great deal of authority over their partners time/feelings/body and expect this interdependence from their partner as well... that would be what I would call a kind of tyrannical monogamy or hell on Earth. The other styles fall somewhere in between, but the classification of your relationship style is far less important than understanding fundamentally how you relate to your romantic partner.
Just wanted to copy paste this post by Marcus here for future reference. Something I've been thinking a LOT about lately.
early forties, straight.