Google does not provide a standard "Chrome OS ISO" for 64-bit systems.
Creating a Bootable USB Drive (Optional) Google Chrome Os Download Iso 64 Bit
Caveats: No automatic updates, no Google Play, limited driver support. Google does not provide a standard "Chrome OS
While often used interchangeably, they are slightly different: no Google Play
What you need:
Chrome OS Flex is a sustainable way to convert PCs and Macs to the Chrome OS environment. It is the official, safe, and supported method.