Putting the substrate and hardscape and hides in, and then dialing in temps and moisture levels, is the better way to proceed. Substrate holds heat, evaporation from substrate moves heat around, hardscape holds heat, hides trap heat, hardscape/hides block heat, heat dries substrate, and so on.
Also, measuring temps with an IR gun is somewhat more accurate and way more effective than stationary thermometers (can measure 20 spots in 30 seconds, rather than one spot with a 10 minute recovery time after moving the thermometer, then closing the enclosure and waiting for temps to stabilize).