With respect to your coop system, after making certain size is more then adequate, make certain you pay attention to details of predator management. The design needs to be strong enough so racoons can not force their way in and digging predators can not dig under. Also make certain roosting and nesting birds can not be reached by a predators muzzle or racoons hands.
If you explore free ranging the flock, wait until they are near adult size. If they are of the smaller or more modified breeds (bantams, Polish, silkies), then free ranging might not be wise unless you have a very competent dog. Also consider managing habitat so birds have cover, especially from hawks. The greatest advantage of cover is that is reduces odds you flock will be detected but if of good quality (which may conflict with landscapers inputs), then cover can be a refuge many hawks will not follow chickens into.