I've enabled vsync so the cpu won't work at more than 60 fps, but is there a way to reduce it further?
Yes, by defining Debug > Settings > Fps > Force Fps to a non-zero value in the Project Settings.
Are there substantial savings to be made between 60fps and 30fps on a very basic game?
Not really. Also, limiting the FPS will make input lag more noticeable, so I wouldn't recommend it. Instead, I would recommend enabling Application > Run > Low Processor Mode in the Project Settings, which only redraws the game when something has changed on screen.