Your Mac Pro knows how fast the internal screen can be refreshed without damaging it. Any resolution and refresh rate you can achive using System Preferences in Mac OS X is safe.
If using an external display, the Mac requires the display to provide its name and its parameters. The settings you can achieve in System Preferences will be within the display's capabilities.
All 13" MBPs only have the built in Intel graphics so you are very limited as to what FPS you can run games at.
As far as the Hz screens run at that has no baring on game play. All flat screen monitors use the 60Hz setting but it really doesn't matter on LCD/LED screens. That is really a Refresh rate for CRT monitors that had to Redraw the screen from top to bottom, bottom to top but with LCD/LED the whole screen is refreshed at once, IE no scanning like on older TUBE CRT monitors.