Q:

Is the past perfect necessary when one action clearly precedes another?

When I describe two actions in the past, one of which precedes the other, when is the Past Perfect more preferable than the Past Simple? 

Jenny put on a mask after I put on goggles.
Jenny put on a mask after I had put on goggles.

I was scared after you yelled at me.
I was scared after you had yelled at me.

After the ghost said, “Hello, children!”, we all screamed.
After the ghost had said, “Hello, children!”, we all screamed.

Which of the sentences, the first or the second, is preferable in the three situations above?

A:

When words like "after" and "before" are used in a sentence the sequence of events is clear and past perfect is optional. So either past perfect or past simple is fine. If you change "after" to " when" it's different:

Jenny put on a mask when I put on goggles = happening at the same time
Jenny put on a mask when I had put on goggles = first I put on goggles, then Jenny put on a mask.

