Yes, Oppo F9 does have the double channel LPDDR4X type of RAM.
No. Oppo F9 is not a water-resistant mobile phone. Be careful !!
No. Oppo F9 does not have the Vooc charger. Though it comes with 10W output power adapter.
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.