Yes, Oppo F9 does have the double channel LPDDR4X type of RAM.
No. Oppo F9 does not have the front camera flash but it does have the display screen flash for the front camera.
No. Oppo F9 does not have the NFC support.
Yes, Oppo F9 does have the GPS support.
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.