not quite. there are two different angles (35 and 45 degree) but the inner diameter of the bearing can differ. Particularly annoying is CK headsets where only their crown races work. You could get lucky but equally you might not.
I mix and match headsets a fair bit and have never had a problem on the bottom bearing. Top bearing yeah as some have a wedge that fits on top of the bearing, some it slips inside.
not quite. there are two different angles (35 and 45 degree) but the inner diameter of the bearing can differ. Particularly annoying is CK headsets where only their crown races work. You could get lucky but equally you might not.