First let me admit that I'm going to respond based on an assumption that you are living in a kind of "on the fence" mode in regard to mono vs poly and which fits you best. I might be able to know you better if I went way back and read a lot of your prior postings - but (spank me) I'm too lazy and time constrained.
But if I'm wrong on this guess it might be good for other readers too to clarify where you are at / coming from with your question.
First I'll pick on the easy, obvious one. You say that 'competition' is still a part of your psyche. And not sure how to deal with it. Maybe try this.........
Equate it to stealing ! (If you are a thief by nature <doubtful?>this won't work)
It's an undesirable aspect of your personality and a serious impediment (and risk) to your own freedom and happiness in the future. You want to embrace that ????? Get rid of it ! Period. Just like you would any other dangerous, risky habit. Totally doable - ONCE you truly realize it's danger.
The other stuff/questions relating to why you might be curious or attracted to others.....
I think that our true basic nature. And it's the part that's programmed out of us by culture/society. Think of young children. Most are totally curious about others and the world around them. But we have to teach them that curiosity can kill the cat and they have to put a check on that.
But you're not a child !
And you just discovered that much of what/why you were told about curiosity was less than accurate. So now some of that curiosity is coming back. But now you are an adult, wiser. Less risk involved (to a point) in that curiosity.
So why the surprise/second guessing ?
You question whether you would have this curiosity if you were in a classic mono situation. But why question it ? Unless you still see some danger or risk.
It's nothing more than my opinion, but I feel we all have so much to gain in so many ways by getting out there exploring the world around us (and that includes people). Yes, you have to be smart about it. But to me, the loss by being a timid little mouse in a corner is an even bigger risk.
Does that help any ?