Sounds lovely. You are not far from Georgia, then. That would indeed be a mild climate. Like southern Oregon, possibly.
Yes, I've used polystyrene sheets like that. I've done a lot of carpentry and remodeling, on four different houses. Where I live now has very cold winters, more like Moscow, so we use a variety of insulating materials. If attics are not used they are often filled with several feet of loose fill cellulosic insulation which is basically composed of paper pulp treated with a flame retardant. There are companies that also make insulation from old denim jeans or even low grade sheep's wool, which comes in batts.