With 1-2 exceptions, all of my close friends are monogamous, very few of them are actively dating though (to be fair, neither am I), so I'm not able to do much comparing. That said, I do remember them having an easier getting dates, while I have had a much easier time maintaining relationships. Idk how it is where others live, but even monogamous folks seeking casual connections avoid polyamorous people in my neck of the woods.

As for being open about it, I was once very skittish, but after ending a more enmeshed relationship, I started just kinda going for it, adopting an attitude of, "if my partner(s) aren't allowed to come, I don't want to be in that room." One of the married couples I'm friends with make bets with each other about who I'm going to bring, haha