Driving three LEDs in series with different Vf at 700mA
It would be more precise to say that with a LED1+LED1+LED2 stack @ 700 mA that you would have approximately 10V Vf.

The Voltage vs. Current curves for diodes are very abrupt (exponential)  it is never a good idea to drive them as if they are voltage mode devices.

If you apply 10V across that stack it is unlikely that you will have 700 mA exactly flowing through it.  So you'd have very poor brightness control as a minimum and you could potentially have it run away from you, depending on the LED's response to temperature and various other factors. etc. etc.