H Believer,
I think a long time ago, you mentioned that one of the important caveats in regard to the use of the past perfect is not to use with such words as 'before' or 'after' and from that, I gather what you meant was that with such obvious time references resulting from th use of 'before' and 'after', the past perfect should not be used like this. Basically, yes. .
I had walked to the post office before last Wednesday. Yes, don't use it like this.
But I have seen plenty of cases where what comes after the words 'after' or 'before' is more detailed like this:
I had walked to the post office before I bought a new bike. I don't see any need to use Past Perfect here. The sequence of events is obvious without it.
Is that how the differentiation is made? No, it's nothing to do with the level of detail.
Frankly, I don't know the clear distinction between the two. Use it if the sequence is not obvious without it. eg
I read a book. I watched TV for two hours. Here, my understanding is 'first the book, then the TV'.
I read a book. I had watched TV for two hours. Here, my understanding is 'first the TV, then the book'.
It's not quite as simple as this, but these are simple examples to illustrate the main idea.
Best wishes, Clive