Open-minded can mean being open to new ideas or ideas different than your own, trying new things, having new experiences, seeking out people who are different than you, whatever it means to you. Just state the sense in which you define it.
If it comes to being open to new ideas and willing to discuss them then probably NPs but if it comes to reconsidering a previously held viewpoint then INJs.
If it means having new experiences then EPs with IPs in second
Seeking out people who are different from you would probably be connected to trying new things so EPs again
I've heard that xNFPs are open-minded, but I've met many anf some of them are, some of them totally aren't. One INFP I know is closed off to trying anything new and pretty much sides with other people's opinions before opening his eyes and realizing what's really out there.
I would be the ultimate open minded person but my Ti is pretty darn developed. Sometimes I have to nudge the Ne aside for a bit and say "yeah, nope. Just..... nope." Though the Fi of ENFPs would probably do the same thing. I guess the most open-minded type is the one that lacks a judging function