What is the "maximum refresh rate" for CRT monitors?

The preset resolution rates are standards which most video cards should support out of the box. The maximum refresh rates are supported by the monitor, however might not be supported by the video card you are using. You need to check your video card's specification to see if it will support 120Hz @ 1024x768. This shouldn't be a problem in most modern video cards, though.

• 800 x 600/155 Hz
• 1024 x 768/121 Hz
• 1280 x 1024/91 Hz
• 1600 x 1200/78 Hz

This is the answer to your question.

It's the maximal "vertical refresh rate" which people simply call "refresh rate" that your monitor can do for each resolution. So yes, you can set your CRT to 1024x768 @120Hz

You might need to tweak your settings in your AMD/NVIDIA utility to access this mode though.