It’s usually better style to use simpler forms when you can. Keep it short and sweet. There are some situations where the difference is important, though.
Take the example:
For more than a year, I wore a mask everywhere, but when I finally saw my parents again, they had gotten the vaccine.
This is a compound, complex sentence with three clauses: “wore a mask,” “saw my parents,” and “had gotten the vaccine.” None of the verbs can be in a different tense without changing the meaning.
The first clause has “wore a mask” because it describes what I constantly or consistently did during a period of time. If I had written, “For more than a year, I had worn a mask ..., but when I saw my parents,” that would mean that I finished wearing masks at the time I saw my parents, and was not wearing them afterward. (I might or might not have put one on sometime later.)
The second clause has “when I saw my parents” because it specifies a moment in time. When had my parents gotten the vaccine? By the time I saw them, that had already happened. If I had written, “but when I had seen my parents, they got the vaccine,” this would completely reverse the order of events: now, I’m saying I was already done seeing my parents when they got vaccinated. Saying “*when I had seen my parents, they had gotten vaccinated,” would be confusing. That just makes it unclear which happened first.
Finally, if I had written, “but when I saw my parents again, they got the vaccine,” that would mean that they got their vaccine while I was visiting them, rather than before.
Another example might be:
I had eaten lunch and was walking home when I heard a loud noise.
The order of events here is much clearer (At the moment I heard the noise, I had finished eating lunch and was in the process of walking home.) than if I had written, “I ate lunch and walked home when I heard a loud noise.” That could just as easily mean I heard the noise first, then ate lunch and finally walked home, or heard a noise, then walked home while eating lunch, or several other possibilities.