Does Safari and Google Chrome for macOS use the same rendering engine?
No. While Google Chrome used WebKit for macOS client at one point, that's no longer the case for current stable build. From the Wikipedia entry for Google Chrome:


  WebKit was the original rendering engine, but Google eventually forked it to create the Blink engine; all Chrome variants except iOS now use Blink


The restriction to use WebKit as the rendering engine for 3rd party Web browser apps exists solely on iOS. From the App Store Review Guidelines:


  2.5.6 Apps that browse the web must use the appropriate WebKit framework and WebKit Javascript.