Hello Massimo Romano,
Maybe I didn’t understand very well but each Clock Enable signal has it’s own control and you cannot use one clock enable for both clocks. However, you may use both clock enables to control the clocks and use them at the same time.
You could use one clock and one chip select on your two RAM modules and leave the other clock and chip select available in case you want to switch to twin-die RAM modules in case you want to increase RAM density.
I hope this helps!
Regards,