Mine move around, they come running up to the door every time I go near them and they also roam around on their own.
I have stood their watching them and in my observations they like to go out and look out the screens and see what is going on.
I also open the door to their pen when I go out in the mornings to feed them and let them come out if they want, you would be surprised at how many will want to walk around outside, especially the younger ones, you can't keep them in if you tried.
I like seeing them get exercise.
I raise mine to have a different life than they would at a commercial broiler house and that includes moving around.
If you don't use a tractor then a pen can be successful if you just put down thick shavings and clean them when they get dirty, I have no problems with using shavings and keeping their pen clean.
I put an extra thick layer of shavings in the area that they like to huddle under the brooder lamp and sleep to keep them comfortable and clean.
I keep the feeder and waterers across the room from the brooder lamp so they have to get up and walk around to get to their food and water anyway. Brooder lamps in one corner, feeder in another corner and water in another.
If you take their food away at night they will be more inclined to get up and walk around in the morning before you bring out their food, mine are all over the place when I go in to feed them in the mornings.
Its better for them if you can get them to move around a bit.