You'd need to know the load of each of the units. My two refrigerator/freezers are rated at 6.5 amps, so well within the limits of a 15 amp circuit. They are both 20+ years old, not sure if newer ones are more efficient.
A 20 amp 110 VAC circuit is good for 2200 watts, a 15 amp is good for 1650 watts. If they both were running at the same time and drew more than the rated wattage they'd trip the breaker. Typically things that plug into a 15 amp circuit are limited to 1500 amps (hair dryers, toaster ovens, Instant Pots, microwaves, space heaters) Modern kitchen and bath outlets are 20 amp outlets, but rarely do you find something with a 20 amp plug on the end of the wire. A plug for a 20 amp appliance would have one of the prongs perpendicular to the other and are why you see a T shaped slot on some outlets.
You'd probably have a bigger issue plugging a toaster or a microwave into the same outlet as a refrigerator than a fridge and a freezer.