Rabbits can get pregnant at just about any time, so it is never safe to have an intact male and female together unless you are wanting to breed. It only takes 10 seconds for mating to happen and that usually will lead to pregnancy.
If he is neutered and she is spayed, it can be safe but there are risks of them fighting. There are still risks with disease and parasites and most are spread when 2 rabbits come into contact with each other or with the pee or poop of another rabbit.
Rabbits don't usually get along and play they want dogs would. Rabbits are more territorial and don't really play like dogs do.
You can try it, but I would not recommend it as you never know how a rabbit will react to another rabbit and they can react differently to different rabbits.