Hi,
Pacing allows you to control the time between iterations. The pace tells the Vuser how long to wait between iterations of your actions.
Think time enables you to configure the think time settings, controlling the time that a VuGen waits between actions. It is designed to help you emulate a real user. VuGen uses lr_think_time functions to record think time values into your Vuser scripts.
You can find additional information about these settings in LoadRunner user guide.
If the think time or iteration pacing approaches zero, or almost none the test will may show higher resource consumption on the server which should increase with the number of vusers used during the test.
The choicing think time settings and Pacing will depend on your business process and the type of test you need: real-world load testing or stress testing.
Kind regards,