Nokia 7.1 Plus and Oppo F9 Pro have similar features and nearly same price. Oppo F9 Pro is just a bit costlier.
Considering the features, Oppo F9 Pro has a bit higher resolution front camera and more RAM. On the other hand, Nokia 7.1 Plus has a better pair of dual primary camera.
You can look at detailed comparison here and choose the one that suits you: OPPO F9 Pro vs Nokia 7.1 Plus
This feature is already there is most phones by going to:
This is really beneficial in alerting without making any sound.
You can also watch below video to help you activate the default feature:
You can check the complete product specs here: Nokia 7.1 Plus
Nokia 7.1 Plus is expected to launch in mid-December 2018. It will have a Octa core (1.8 GHz, Quad Core + 1.6 GHz, Quad core) Snapdragon 636 processor coupled with a 4 GB RAM.
Specs: Nokia 7.1 Plus