As far as the 1.23 vs 1.3, it is in the certification of the aircraft under FAR part 25. If I recall it 1.23 is used if the aircraft has a stall pusher.
In the real world, Vref is a factor of A/C wt, A/P temp and A/P altitude. Then modified with flap selection and wind factors. Vref corrected by wind normally is never greater than Vref+20.