Would anyone know how to achieve this effect in photoshop?

Hello,

What do you mean, how to create a professional collage? The video shows the steps... Or am I missing something?

I don't see any special techniques in it, and in saying that I'm not putting the result down - I like it.

You need to learn about making selections - he used the pen tool in the video to create a path ( I would then use masks rather than cut-outs as used in the video - as masks can be adjusted later)

Layer effects

Building up layers

Adustments such as Threshold - again I would use the, non destructive, adjustment layers rather than adjustments

Dave