Luckily I have five conures in the bird room...so they are the same size pretty much. They usually keep to their own areas. B&C can be wanderers, so I just put up a mosquito net curtain to separate them from the others. When they are out together I am always checking on them as they are flighted.
In our family room are the larger birds and Jade, our sennie....she thinks she is a big bird! lol Plus she came with Chopper, our CAG, so they needed to be in the same room. Apollo, our mealy, and Chopper can be out at the same time and both keep to themselves...they show no interest in each other at all...knock on wood. I usually wheel Jade into the sunroom and let her out with the door closed. If I am in the room, she can be let out where her cage is but she prefers the windows! Nani is always with me wherever I go...kitchen, bathroom, living room, sunroom, bedroom, third floor, etc.....
My two little ones Kiwi and Dozer are kept upstairs and I let them out only when I can give them 100% attention, usually on the third floor or in my bedroom...both of them are flighted.