Braided Brake lines

There is no reason to use the wrong flares especially on brake lines.
There are adapters which will seal the lines properly.
There must be enough length so the tightest curve is above the minimum radius allowed by the manufacturer. Otherwise it will kink and eventual fail.
Just because it is an AN fitting or hose does not mean it meets aircraft specs. At one time, yes, but those days are long gone.
DOT approved braided lines - there were some available - don't know if they still are
Most use of braided brake hose is for road racing and similar as it doesn't expand as much under pressure which translates to slight improvement in pedal feel- which can get critical especial late in a race.