Heat dries out the humid hide faster, and it can increase the overall humidity of the tub to a higher level than it should be. If you do heat it and don't have problems with these, then go for it.
With the moss hidee do y'all give heat to the container.. i made one like in the pic
Not directly. Our rack has belly heat so some times they move the hide over the heat. I do put the hide on the warmer end of the tub though but not necessarily over the heat. Also, when they start a shed cycle I make sure the moss is damp but won't drip when squeezed. After they shed I usually let it dry out till the next shed cycle.