As I recall there is a big difference between replaceable blades and not so much the handle they go in. And having said that a straight should shave just as well (most of us think better) than a replaceable blade. I went through the blade thing playing around with a double edge.

If you target a Kami make sure you get a western grind. Traditional s are made for a barber to use with one hand and so one side has a different angle on the edge if any at all.

Sounds like your learning fine, just short on patience :<0)