Man, my friend was convinced his icons looked off. He finally tried changing just one line to be thicker, and the whole thing suddenly had weight to it. That tiny fix changed his whole approach.
That idea about stroke width making icons pop really depends on the style. I've found that keeping lines uniform often looks cleaner, especially for simple system icons. Messing with the widths can sometimes just make things look messy instead of adding depth. Maybe it's about what you're going for, but a sharp, consistent line has its own kind of impact.