Screen flicker is an entirely personal thing - some notice flicker as low as 85Hz, others barely notice it at 70Hz.
As a general rule, the higher the refresh rate the better, in terms of reducing eye strain. Note that you should not exceed the capabilities of your monitor, or you will damage it.
Screen res is the resolution of the screen, i.e. the number of dots that are crammed into the available viewing area of your monitor.
If you are running XP, it will default to 800x600, that is, 800 pixels (dots) across the screen,and 600 rows vertically.
The higher the resolution, the smaller each icon will appear on screen, and the more you can view of a spreadsheet, document etc.
Again, your monitor will have a maximum resolution - do not try to exceed it.