Which vaporizer machine is better to help with stuffiness, warm or cool? difference?

No real difference: more like there isn't a big difference between the two. dehumidifier is simply used to add moisture to the air, this is helpful in the winter when the air is dry. a vaporizer is specifically used to deliver a humidifier medication into the air such as Vicks Vapor solutions. if you're going for moisture humidifier will be sufficient.