Hello, there is a substantial difference in the filling from one side of the duvet to the other side. A 10.5 tog duvet is more than suitable for all year round use in a modern home.
Hello, yes they can be machine washed and tumble dried as long as you have a big enough machine like you find at the local laundrette to dry completely dry out the fillings,
Hello, the difference in the appearance depends on how full you have the filling on one side compared to the other side of the duvet. a 13.5 tog vs a 4.5 tog will look fuller on one side.