I understand that part of the HiD, I was just wondering why he wanted that shade, personally I would have used something closer to the shade my headlights ran.
but also, like you said, the yellow color is better suited to poor weather, so I can understand using that.
I also sort of understand the difference of H1-H3.... just not fully yet, but I am getting there, doing a lot of reading up on it

I believe H1 is designated as primarily main lamps, while H3 would be more along the lines of secondary lamps such as fogs ? (no clue about H2/H4 yet)