I am using an old fridge/freezer, I start the brew in the freezer first 5 ~ 10 days, then move to fridge for next 5 ~ 10 days. I find the fridge gets no cooling but in North Wales after the first 5 ~ 10 days it does not need cooling. The freezer is frost free, it has to be, or it will have the evaporator as shelves within the unit so can't get a fermentor in. Since frost free there is a built in fan, and the evaporator is behind a panel at the back, so once power is removed cooling stops straight away, there is no mass of stuff causing the cooling to continue. With the sensor on the fermentor under a sponge so not reading air temperature the unit will run when first switched on with a fermentor at 23.8°C for around 40 minutes before switching off as fermentor hits 19°C. At this point air in freezer at around 8°C. It will warm up again quickly and start a second time before settling down as the plastic wall of fermentor not that good at radiating heat even with a fan running. After this it will likely run twice a day.
Without the fan it would clearly take longer to cool down, and with a chest freezer you also have walls made of aluminum not plastic with the evaporator in contact with the aluminum so after the motor switches off it is still cooling the brew.
Since I don't use a chest freezer I don't know how that changes how it works? Heat side I just use an 8W bulb, even in the heart of winter in my garage that is enough. Now here I in early days made a mistake, I used a demo under floor heating tile 18W which the fermentor sat on nicely. However mass matters, so when it turned off, it was still heating the brew, also 18W was too big so the tile got too hot, the net result was the temperature would over shoot. Ambient temperature in garage 2 ~ 26°C winter to summer. I am sure in USA the swing is much greater? But still learn from my error heater needs to be light and small unless using a fish tank heater in the brew.