The perfect, trembling lines of CUB STIDIO

[Paul Esteves]

I just watched their showreel, do you mean at 35-37 seconds?

https://www.cubstudio.com/showreel/

[Charlie Hughes]

Too funny, the effect is in virtually all of their illustrated videos but in the demo reel itself it’s nearly invisible.

it’s subtle but constant here:

https://www.cubstudio.com/bill-maher

Same but cranked up higher here.

https://www.cubstudio.com/the-never-ending-party

Same but they opted to turn off animating it here, leaving it as a static ripple to all the artwork . This was the clue for me in figuring it out.

https://www.cubstudio.com/cadimage

And finally here’s my closes approximation (though a bit excessive as it’s cranked way up.)

https://vimeo.com/123050628

[Ace Billet]

Roughen Edges will do the trick.
IIRC animating the Evolution property will make it jiggy with it.