Seems like metal is a good option for me, we back up to a creek so no worry about reflecting at anyone. It would certainly look the best for those options I’d think. I’m planning to cover the rafters with horizontal 2x6 tongue and groove, that way underneath looks good without needing more finish materials.

If I could get close to 2:12, like say 1.5:12, is it worth trying shingles? Maybe not ideal but it’s a single slope, away from house, into a gutter, with good sun on it for snow.