On the iPhone Xr power + volume down brings you to the emergency call screen and disables faceID. Technically either volume button works, but if the phone is awake power + volume up just takes a screenshot. On my Xr with apple pay enabled mashing the power button 5 times just brings up apple pay, puts the phone to sleep and then wakes it back up.

I'm not sure if it's the same on other iPhone X models.