Ball Python?

yes, i dont have a basking light for mine, just a heat mat. just remember even though balls are nocturnal, all reptiles need to know when it is day and night. no uv lighting is required but a lamp or natural sunlight through a window is ideal for 8 - 12 hours a day. so even though there is not going to be a heat lamp for light, just make sure to provide "day time light" however you can. a single heat mat to my knowledge cant be more powerful than any other single heat mat. they all put out a high amount of heat. it shouldnt be assumed that a bigger one rather than a smaller one is "more powerful" one just covers more suface area than the other but they all heat up to the same temperature.

Yes a heat mat will work fine. Ball pythons dont require any lighting. It should be placed under one half of the tank. Make sure you provide a hide box on that side, and on the cooler side so your snake will feel safe while regulating its body temp.

No, ball pythons need UVA rays from the sun and a reptile bulb can provide them with the UVA rays. They need light and a heat mat cannot provide that so you will need a bulb for your snake. What would it feel like if you were kept in darkness all your life? Don't you think your snake would like a little bit of light even if he's nocturnal.

Yes Ball Pythons are nocturnal, so a light is not necessary. A heat mat will do fine.