Most of the heat-fan-light combos I have installed also have a nite lite so they are 4 function. They are mostlyNutone brand and come with switches that are back stab only-no screw terminals. I never use the supplied switches. As for wiring them, using 12-2 and 12-3 NM cables can get real crowded and you end up with an extra conductor or two. If it's new construction I like to use 4 steel boxes ganged together for the switch box. I feed 2 circuits to the switch box, one for the heater and one for the fan and lights. I then like to come out of the switch box and go up with 1/2" EMT to a 4x4x2-1/8" j-box on top of the plate. I then go the rest of the way(usually less than 3') with 1/2" flex to the fan/heater/light. I pull 2 #12 neutrals, one for the heater circuit and one for the fan & lights, one #12 ungrounded conductor for each function and a #12 green all THHN. This may seem like a lot of trouble but it makes for a more managable situation in the small wiring space the fan/heat/light provides and avoids extra conductors or re-identifying conductors like when using a combination of NM cables.
