Yes a bonded pair will interact, they will sleep, eat, and play together, and groom each other. Unless you are emotionally and financially prepared to breed then you want a same sex pair, even if just together for playtime breeding can literally take seconds or less, too fast for you to separate. You can have one of them neutered but personally I think it's a bad idea, the operation is risky since they have to be put under and can include lots of post op care and complications. There is really no telling if they will get along forever or not, it's kind of like people, just because two people are friends doesn't mean they will be forever. Also unless they are already a bonded pair then there is no guarantee putting two chins together that they will even be friends in the first place, some chin's just don't like company in the cage. I have however had chins that live in separate cages that enjoy having playtime with each other, and living next to but not with each other.