Can you record Face and Screen Capture simultaneously as two different video files in iphone
Yes, the iPhone is able to record two videos simultaneously.
But no, I don't think there is an app that does what you want. As I understand it, you want to do screen capture of any app, and simultaneously record the front-facing camera using a different app, than the one being screen captured. That is not possible.
You can do screen recording of any app simply by using the built-in screen recording feature of iOS.
You can also record using the front-facing camera at the same time using the built-in Camera app, or any other app that offers video recording. You can probably get an app that will record without actually showing the video on screen.
However, you cannot then switch to a different app (for example a game) and have the camera keep recording in the background.
If you do not want to use two devices to be able to do this, a work-around could be to record the screen capture first, and then record the reactions after the fact and edit them into the video. This is how some Youtubers add small reactions to their content.