From my experience, I do not mix clownfish species. I don't even have more than two of the same species in a tank. Can you mix clowns or have more than two? Yes, but they will fight. Having multiply species in the same tank is like two rival gangs in the same area. Eventually, something happens. My lesson was, my maroon female chased my black ocellares out of the tank and onto the floor.
I have also had five of the same species in one tank. What happens is the largest two become a pair and beat up the smaller fish. The smallest eventually died because all the larger clowns picked on it.
If you just have a pair of the same species they act like two kids in love most of the time. It is cute.