I'll add my experience here. I have two fridges, both controlled by Inkbird 308 and both have a 45w tube heater in them. One is an under counter fridge and the other is a larder fridge. The under counter fridge is used for fermenting at 20*c in my garage, and has no problem maintaining a steady temperature even when the temps in the garage drop to just above freezing. The larder fridge is used for serving at 12*c and again, I have no issues with the heater or controller. I also just let the probe hang in open air inside and do not have any fans. I don't have problems with the controller overshooting or constantly cycling from heating to cooling.
Jas