What thermostat are you using now? I would usually recommend a herpstat the new model intro+ would be my first suggestion the right price with some of the most advanced safety features on the market.
What are your ambient temps? I would use a UTH as a primary and it is possible with a light added to the enclosure you will not need any other heat source. Fluorescent light and deep blue LED.
Depending on the Viv you may not need the CHE. Fluorescent lights mounted inside often run around 100ºF this is often enough to heat the enclosure to correct levels depending on the type and style. At night a blue LED they type used for aquarium. The led don't put out too much heat but the transformers do. They often run into the mid 90s often this will hold ambient temps over night. CHEs work fine but they get very very hot and if there is a simple low heat option personally I prefer that.
...I moved mine from tub to viv about the same age .... i use a rhp and small uth for belly heat with a vivarium electronics thermostat my temps and humidity are great ....my snake is also kept in a room with avg temp of 70 degrees