Clip synchronization options greyed out

Hi there,

Perhaps I'm too used to Adobe's PP, so I couldn't figure out how to align (albeit manually) three clips so I could PIP them. This video explains how far I got: https://www.youtube.com/watch?v=vORZai3Rvp4

Multicam clip seemed the only way to synchronise them at first but the Angle editor doesn't seem to allow me to overlay different scaled down videos upon each other!

Thank you in advance for any tips,