transported animals many times for longer distances including for 8h+ drive too

that is how i do it. I have a climate controlled box, made out of big styrofoam box, + ducktaped heat cable on a walls that is attached into thermostat. also I have a digital thermometer/hydrometer attached, probe inside, display outside, so i can check on things without opening a lid and messing out with climate. i take this box into a car and plug into car adapter, i believe it is called inverter. for humidity i just spray it and check the readings, usually for 8 h drive if not to open a lid, one or 2 of good sprays is more then enough.

then i pack animals in whatever smallest size KK i can or appropriate size plastic bin with holes for ventilation. then, assuming animals need about same temps/humidity, i pack them into my box, take it to the car and have no worries about anything. oh and you need to make sure nothing is gonna shift inside, so i put some fillers inside if needed and make sure the box is as steady as can be in a car itself.

if you put animals in a KK directly into the car without anything else, AC going on, doors opening and closing, ability to see around, it all stressed them out and you can"t ensure correct temps and humidity, chances are nothing will happen, but I personally had too many things going on to take any risk chances. and say if somewhere you stay in a hotel you just unplug the box and take it inside and plug it into the wall, and in am you take it back to the car and plug it in.