Show welcome screen when starting controls whether the software just starts up with a new project and a blank screen, or whether it shows the friendlier Workshop selector.
When you select an option in the Workshop selector, you are then asked whether you wish to start a new activity, return to the main screen, or (for existing workshops) review previous activities. You can turn this off in the workshop selector, and can re-enable it both here and by holding the Shift key as you click to make your selection. The two options in this dialog allow you to control each individually.
The "Confirm when closing Impact Explorer™" option allows you to disable the confirmation dialog that appears when you close Impact Explorer™. This is normally done to ensure that you don't accidentally exit the software mid-workshop, but can be disabled here.
The spelling options button allows you to configure aspects of the Impact Explorer spell checker. These options are also available when the spell checker finds a word it does not know.