Picture in picture (facecam) with video recording with Ps4?

I would like to know if and how the title mentioned works. That I can take a picture in the picture with the facecam while recording with the ps4 (not streaming) at the same time. I know when streaming that.

or do I have to record my face separately on a pc and put it together afterwards? Which I imagine quite cumbersome since the reactions have to fit exactly.

I want to upload a letsplay with facecam to youtube, but I'm a console gamer.

I'm happy to help and have been as detailed as possible.

Yes, you cut it together.

Often, picture and sound are recorded separately, which is also cut together. In order for this to work, you usually make markers, in film it is the famous mouth, but you can also clap your hand or something, then you have the clap on the video track and then align the clap on the audio track, finished.