When playing lead guitar, whenever I had to play something fast, usually using alternate picking, I was only focused on the timing and not playing sloppy. When it came to tone, I only worried about my amp settings and guitar volume. But what I realized is that I was picking pretty hard which creates this harsh tone sometimes. I started to consciously pick a bit softer and make sure every stroke was consistent, and now my fast licks sound much more professional.
Another thing I realized because of this is when playing with a very clean/acoustic tone, the higher strings are naturally louder. So when picking across all the strings (like arpeggios), I know make sure to actually pick the lower strings harder while picking the higher strings a bit softer. This makes the overall volume more consistent.
Anyway, like I said I'm sure a lot of you have discovered these things already. And if you have any advice to add, I would love to hear it. Thanks!