iOS app for editing IG Stories videos (picture in picture, 2 videos at once)

I'm noticing a growing trend of people using some app to do picture in picture or 2 videos at once in their Instagram stories. It gives it a nice touch and unique content should drive more watches (and link swipes on stories).

Would anyone know what apps are being used for this?

I note a lot of fashion bloggers produce the same style, so I assume there is a common app. Some examples (while they have stories online obviously) of people who use such an app for some of their stories;…

iOS app for editing IG Stories videos (picture in picture, 2 videos at once)