The compute module by design is wired to either use the internal Embedded MultiMediaCard (eMMC), or a Secure Digital (SD) card, which is the successor medium to the MultiMediaCard and is similar at a signal level. This isn’t a limitation of the uConsole but a side effect of the way the compute module is designed. The same is true if the CM5 is placed in any other carrier board; only Lite SKUs can use the SD card slot.
Peltier modules are semiconductors that, when powered, move thermal energy from one side to another, making one side cool and the other side hot, but when the hot side reaches its heat capacity it will overheat and melt internal components, effectively self-destructing. A Peltier module used in this fashion will have a significantly shortened life span.
The cooling module you have may well be a Peltier module, but it also has a good amount of active heat dissipation in the form of a fan so the module doesn’t overheat. Using the fan alone would be significantly more efficient than using it alongside a Peltier module because the electrical energy used to power the semiconductor to apply the Peltier effect would be dissipated from the circuitry in the form of heat energy, making the system as a whole hotter.