The device here lists 1.65 V-2.2 V and 4.5 V-5.5 V, but not 2.2 V-3.6 V. If I want to run the device at 3 V, should I use the 5 V value as a reference?

Comparison between the two as seen from the Logic Block Diagrams & Pin configurations as shared here in  gives one to understand , there is No difference between CY7C1041GN & CY7C1041G .

NC Pins in both CY7C1041G & CY7C1041GN are Not Connected Internally to the Die.

CY7C1041G is supposed to be a part with ECC, while CY7C1041GN is identified as No ECC  as for the PCN . Confusing indeed!!!!

Sharing extract of  PCN155107  Last Updated: Oct 31, 2017,   Issue Date: December 20, 2015,  Effectivity Date: December 20, 2015

4Mb FAST and Micropower (MoBL®) Asynchronous SRAM Products: Technology Transition from 250-, 180-, 130-

and 90-nanometer to 65-nanometer Technology shared for ready reference provides the details of Process migration.