What kind of flour is needed for strudel/fillo dough?
Your best bet is a stone ground bread flour or hard flour in the US that means finding a local mill. At your standard supermarket a high protein bread flour is your only option if you can find it there. I generally have to venture out to a Whole Foods market to find that as my "local" grocery store doesn't carry it. You could also try Tipo 00, I have run across it in some specialty stores. You are looking for the highest gluten content you can find so that you can get the elasticity you need to make proper strudel.