I find it hot both ways. My primitive brain likes promiscuity, my conscious brain likes an exclusive couple. It tickles different things.
I can say that once couples open up they almost invariably lose something, particularly when they enter the OF club of whores and pimps. They lose themselves in the act. They get tattoos, they get surgeries, they fuck around without any passion or attraction. They become normal performers just like anybody else. And often the couple fucking implodes like it happened with Hulk and Isa. Isa now is just a porn actress, I'm surprised she's still natural and mostly without tattoos. I didn't understand if Poppy got a boobjob, there's a specific clip that made me think she did, but otherwise she still seems to have the same old tiddies. If it's a boobjob, it's subtle enough not to destroy my enjoyment, but it's a bad sign in my book.
Some couples who open up preserve their magic, if they do it in a way that still takes into account the realness of the act. Poppy and Zach seem to have preserved that, they have sex with the same couples, like Pricess Rae. They aren't excessively promiscuous and fuck just anybody with the right lawyers and contracts.
I think one couple that might end badly is Catandthebat... I think they're getting in the wrong loop.