So in summary the from all the posts above:
- There are slight differences between models
- SPD INTV activates VNAV SPD before the criteria of the VNAV Approach Logic are met
- VNAV PTH remains enganged when the VNAV Approach logic criteria have been met
- The open SPD window enables/allows manual adjustement and control of the speed
- Closing the SPD window will allow VNAV to control the speed, based on actual flap configuration and preselected VREF additive to selected landing flap when set
- Flight directors will guide you down the calculated VNAV PTH until recycled from view
- Flight directors can guide you down to ruway or MD coded waypoint
- Flight directors when crossing this last point can/will command the missed approach pitch/turns (slight difference between models) or remove from view until TOGA selection