Keep in mind the computer fans generate a small amount of heat which also must be removed by the fridge.
Computer fans vary widely in the amount of air moved, for the current consumed and the noise made. Some companies Like Noctua make incredibly sophisticated fans. I employed one of their 120mm fans on my condenser that makes half the noise and uses less than half the current as the fan provided with the fridge.
For my interior fan, with my small 1.8 cubic foot compressor fridge, I sought out the 40mm fan with the least current consumption, at 0.03amps. It moves about 6.5 cfm. I have it blowing at the evaporator/coldplate 24/7, and it makes a huge difference.
Much more even internal temps.
A lower thermostat setting needed to achieve sub 35f everywhere in the box.
Much faster cool down of warm items placed within.
I took power from the LED light for the fan.
I would not want to cycle the fan as the hydro dynamic bearing lubricant was never intended to start in such cool temps. So far the fan will have been running nearly continuously for 2 years.
A similar fan (with a sleeve bearing) made it 5 years before becoming noisy, in my last fridge which failed.
So keep in mind the fact that not all fans are created equal. Huge variances exist in design and performance, and larger fans moving lots of air inside the fridge could easily negatively affect overall performance by adding a heat load, or by expelling cold air more efficiently whenever the door is opened.