rack vs. cage depends on personal preference so i'll just discuss heating. a properly wired rack only needs 1 reliable thermostat. for an enclosure like a T3 or T8, it depends on how many heatsources u are using. if u are using both a heatpad and a radiant heat panel, u would need 2 thermostats or something like a Heprstat 2 that could handle both.
and here's a tutotial on how to setup a PVC age (AP T8): https://ball-pythons.net/forums/show...-With-Pictures!