They all can be left loose in the house but they're rarely, if ever, all left loose together.
It USED to be that Fudge, Taz and Scamp were locked in my room, Aura and Diesel were crated and Tika and Ozzy were left with the rest of the house. However Diesel destroyed his crate and its not suitable for anything other than feeding him in any more and Scamp is now crated for his own safety.
So now if we're only be going to be gone for a short while and the weather is nice, Diesel, Fudge and Taz are left in the yard and Aura, Tika and Ozzy are left loose in the house. Aura chews zippers and Tika steals food, wrappers that may have contained food, etc as well as torturing the cats but she behaves a lot better than when she's crated.
If we're going to be gone for a longer period of time then Fudge and Taz are confined to my bedroom, Aura will probably be confined to the kitchen and Diesel, Tika and Ozzy will have the living room. The main reason for that is that Diesel has discovered how to jump out the kitchen window and does so any chance he gets. Plus between Tika and Diesel no one is getting into our house. Ever. When we left them for a day, our uncle was supposed to let the dogs out and they refused to let him into the house and they wouldn't go past the doorway, just stood there barking at him. The reason that's good news is that I may have accidentally broken the key for that door so it can't be locked any more.