Selenium, how to control the execution speed of the test?

Have you tried using the "setSpeed" or "setTimeOut" commands?

They basically serve to control the time and speed of running scripts.

Link to more information about:

Use implicit waits to control the execution flow. Putting sleeps is not a good practice because it really hurts the test suite.

With the implicit waits (waiting for an element to appear, waiting for the page to load), some command will not run before the context is ready.