I think all rod types are a bit different. My main rod is a 6wt, that seems to throw light weight dries better with 5 wt line, however works best with hoppers, and nymph rigs on 6 wt line. Meanwhile I have an Orvis 9wt that has to be overlined 1 to 2 sizes just to cast farther than arm's length. But once you get a powerful enough line, boy can that rod scream out the line.

I wish there was an easy way for me to test cast various lines with each of my rods to help find the sweet spot. *sigh*