I have a few breeds of bantams. Belgium D'uccles, Serama, Game Bantams, Silkies, as well as a few mixed bantams.
None of them sleep in trees, and even if they did it would not be smart to leave them out all night. They're easy prey. You'll definitely need a coop for them at night.
My Belgium D'uccles are by far my favorite. They're the sweetest little things, cute, lay pretty well, and get along well with my standard size birds. They also listen well when our rooster sounds an alarm saying there is a hawk in the area. They immediately run for cover. I've still had one taken by a cat and one taken by another unknown predator.
My Seramas and Game bantams drive me nuts. They're so skittish and completely ignore my roosters warning sounds.
My poor Silkies are adorable but I'm not sure they have much of a brain. They always act so confused, and wander around aimlessly. Plus they can't see well with their "head fluff" so I've had quite a few of them taken by predators. Everyone has always told me how sweet silkies are but I've never had one that acts any different than my other breeds. They run away when I try to pick them up just like everyone else. Only Silkie I have that is an exceptional bird is my Silkie rooster. He's the best rooster we have ever had.
Hope you find what you're looking for but make sure you don't plan on having any breed of chicken sleeping in trees. My guineas sleep on top of the coop sometimes when they're being stubborn but they are exceptional flyers.