A radiant heat panel (RHP) can be either top or side mounted. As in the name, they radiate heat without the drying effects of a CHE. I will use one for each of my big boa cages to increase ambient air temps. They are also good for arboreal critters who benefit from overhead heat. In your case, you would be using one to bump your ambient temps without decreasing your humidity as drastically as a CHE will.
All this said, there are many ways to set up an environment and they all work to varying degrees. A lot depends on the money you have to spend and the time you are willing to spend 'tweaking' the environment on an on-going basis.
I strongly suggest using tubs or a reptile cage for the best environment for your snake and ease of use for the keeper. That said, I realize people will continue to use fish tanks and they will continue to make them work for themselves and their snakes!!