Another question, Will I be able to let them free range in my garden or will they fly away, the other day I saw 2 chickens on my neighbors roof . or will they eat all my veggies.
They will not fly away- but they will absolutely lay waste to your yard. You will want to keep them locked in a coop and run for sure. There is no if- they will destroy everything within like 100 feet that you don't want them to destroy!

If you are getting them for fun or just eggs for you... maybe just go small lie you said. 6x12 is plenty of room for 4 birds, and probably 6 if you keep it clean.
Good luck!