Make sure they have enough room so they can get away from each other if they need to. And that there is no where one can get trapped - so each hidey needs to be like a tunnel. If you have hideys with only one doorway or a cave area these can be flashpoints. And 2 food bowls / water bottles so there is no tension for resources. That way you can tell easier whether their problem is with each other or just feeling worried that the other will stop them getting food or rest! It sounds like they are having some nice 'getting to know you' moments as well as the dramatic ones!
I brought in a pair of females for company for my (neutered) male, had them as neighbours for about 5 days, and put them together in a neutral pen. The dominant sow decided she didn't like him and it became very obvious very quickly. Within 10 - 15 minutes she attacked him and there was a proper fight, rolling around the floor, and this happened twice more until he ran circles squealing while she chased him and I had to throw a towel on them. Yours don't sound so bad!
(PS. He now has a friend of his own ☺)
) 
