If a loaf being used for lechem mishnah is wrapped up or in a bag, is it best to remove it before using it?
The Challah should ideally be removed from the bag before the bracha. The Mishna Brura quotes various sources that one should have his ten fingers on the bread as he makes the bracha and therefore should remove gloves before a bracha on bread. The same would apply to a plastic bag. See Mishna Brura 167:23 and 271:41.