Brake lines sizes/flare types

The threads in brake lines are called tube threads. They are straight threads, just like a bolt. They are not pipe thread. They don't have a taper, since the flare itself does the sealing. There's no real set standard as to what fitting size is used with what size line although there should be. In other words, you could have 1/4" brake line, for example with a 1/2" thread tube fitting, or 9/16, or whatever. Whatever fits your master cylinder.