There is no difference between 59 Hz and 60 Hz, in terms of performance. Both 59 Hz and 60 Hz are translated to 59.94 Hz before they are sent to the monitor's chip and should, therefore result in identical performance. The reported 59 Hz setting that cannot be changed even after tweaking the display settings is a result of how Windows reports signals coming from a monitor that uses the old TV-compatible standard of 59.94 Hz.
For backward compatibility, Windows keeps the 59 Hz setting for applications that use the older standard but also reports the 60 Hz setting for applications that require it. You may refer to Windows Support for more information.
