I totally agree with the temp gun recomendation

but you will always have to play with the temp and usually it’s always going to be higher than what you really want it to be because the probe is on the outside pressed right against the heat. It now has to go through glass or plastic or pvc to then heat the other side of the cage.

I have a few different types of cages and they still all need to be a bit of trial and error to dial it in. You always want to take the temp right at the surface of the cage not the substrate because the snake will move that.

Great job testing things before you snake arrives as well.