100% pilsner malt for both Helles & standard German pils beers. I'm thinking both hopping rate and water profile would be key differences - higher sulfate level, sulfate/chloride ratio tilted toward sulfate for a more hop/bitter accented pils, with something like a Munich water profile being more standard for helles. As I say, this is what I'm thinking, but lord knows I'm not the smartest guy in the room. I haven't experimented with different maltsters to compare grain flavor contribution - Weyermann is what I have easy access to. I love the rich flavor and "softness" of a well-brewed helles but have not attempted to brew my own yet - that's on the one of these days agenda.