I have two male dogs - first one is 2 years old and the new one is 8 months old. They fight 'n play... all the time.
I don't get involved unless I hear one of them YELP. Then I'll step in and admonish them slightly but I leave them to work it out. They need to work out who is the alpha dog (after me).
They do also get their own quiet time away from each other too where they can see each other but not interact (when the pup is in his crate or separated by the crate in the kitchen). I rarely let them run around the whole house since Littlest Mac is not fully house-trained yet (almost but not quite). So they play together under my watchful eye in the kitchen only.
