Don't worry. There's a take-away at the end of this that should clarify what I'm writing. It ain't easy to describe musical concepts in words, and my literary powers are under a cloud today anyway.
So:
What are the most important notes in this arpeggio? The log F? The high C?
Neither. They're all important.
But many people treat the notes between the first and last notes of an arpeggio passage as throw-away notes to get past to reach the ending note of the passage.
The next example is similar, but not identical. People generally play the arpeggio into letter D correctly, but when they see the arpeggios with the 32d notes, they treat the 32ds as throw-aways, to get past before the "important" quarter notes.
And with runs, the same thing happens, as in the third bar of this example:
In runs especially, the notes are often treated as mere ornaments to get past to get to the important stuff. Also, in runs like this, people generally don't make any dynamic change at all as they go. (Or worse, they play all of the notes softer than what surrounds them.)
If they vary the dynamics at all, they generally crescendo in the very last few notes, but play everything before them at the same dynamic level, often less than the "major" notes surrounding them.
Might that be because they're printed small? Maybe.
Well, the "middle notes" in both runs and arpeggios are important, and they should be treated well. They should be supported in the middle with the same or even greater breath intensity as everything else, actually playing them with a small crescendo and diminuendo so they don't get lost!
All that, and the windup and pitch amount to only two things:
Support all of the notes in fast arpeggios and runs. They are just as important as the beginning and end of the string of notes.
Slightly crescendo and then diminuendo through the whole run or arpeggio. (If you just think about doing that, it'll usually happen automatically.)
I sure hope I made sense here. I'm not sure I did, but you got what you paid for.
Cheers!