Yeah, the pad should cover 1/3 to 1/2 of the tank. In a 10 gallon, that should be all you need for heat, but that depends on the type of substrate you use and how thick it is. In a larger tank, you may need to supplement the heat with a lamp. We use the infrared ones for our snakes. They put off heat, but the light doesn't bother them. Being nocturnal creatures, too much light can stress them out.

Smulkin made the homemade humidifier for his red blood python, and it does a great job of producing and maintaining humidity.