Yes, Oppo F9 does have the face unlock.
Oppo F9 has the aperture of f/2.0 for its 16MP front camera.
Yes, Oppo F9 does have the double channel LPDDR4X type of RAM.
Oppo F9 has a dual rear camera set up, 16MP and 2MP. The main 16MP rear camera has an aperture of f/1.8 while the second 2MP camera has an aperture of f/2.4.
The most striking feature of the Oppo F9 is the big display with the waterdrop notch. It is well designed, delivers good battery life, and offers decent performance for the price.