I just looked at your photos, and the coconut coir IS what you are using as a substrate. This type of substrate LOOKS good, but I would not recommend it for a Ball Python. As I stated, it stays too wet and it will be difficult to keep clean because you will have to break down your tank every time your snake defecates or urinates just to make sure you get all the contaminated substrate cleaned out. The aspen bedding or just plain old paper towel will make life much easier for you. I use the coir for my Pacman frogs. It does help with the humidity, but they like a moist damp substrate.
There are tricks to help maintain the humidity in an aquarium type enclosure. One is to cover most of the top of the enclosure with something to keep the humidity in the tank. You want some air flow so it doesn’t become stagnant and you get mold growing. Live plants help as does putting the water dish at the warm end of the enclosure. I also mist the inside of the tank about 2X a week. More often when he is about to shed.
You have ONE HANSOME snake there too. Beautiful!!!
Listen to him. He’s telling you he doesn’t like the substrate.