Yes, they may still fight if they are within sight of the hens. They do better if they can't see the hens at all.
With ours, sound does seem to play a part but not nearly as much as seeing the hens and/or another cock. We moved one of the groups to the back pasture to be near the garden area and do some un-supervised free ranging. They can all hear each other and the groups in the front pasture can still hear the two cocks in the back pasture crowing and the hens cackling, but the cocks penned in the front don't seem to get very excited unless the group ranges up to the front of the house where they can actually see the hens and the other cocks.
Nope, mine have been known to lay in the middle of the floor or outside on the ground if a nest box wasn't available when it was needed. You can use a cardboard box or a basket for a nest box. Just put it in a corner with some hay, straw, pine shavings or something else for nest material.
