The Sharp edge thing, I go with the flat so I dont worry about cracking, I have found no rpm difference, but that is relative anyway.
The steel on this one is 8620 (oil quench) Very easy to machine in annealed state
I made another out of S7 steel. air hardening. I heard good results of it, The stuff is difficult to machine though in the annealed state.

As far as the material on the AP crank, I have no idea, THe norvel's measure 57-60 crc so I know their stuff is good. I never tempered them softer. (cant go harder)
I have no clue what material the norvel is either.
Having fun