"-The reason changing pick angle and power works is because different angles make certain frequencies within the note louder, therefore changing tone. "

Yep.

Try seeing how many ways you can play the same note.

Pick it hard
Pick it soft
Pick with your fingers
Bend into it
Release a bend to it
slide up to it
slide down to it
Pinch pick it it
Fast vibrato
Slow vibrato

You can play kick'ass blues with just a couple of notes if you master using all those techniques to make different "tone".

Notice how many different ways Stevie could just hang and wail on one note and get different "tones" out of it.

Peace,
-Rico