… Can I do something like the below video with Motion 5 (overtop of existing looping backgrounds for example)? …
Motion5 is a tool which allows effects/animations like this, but wether YOU can do that, I can not answer
M5 is an awesome powerful tool, although with an hobbyist price-tag meant for professional users. it comes preinstalled with -zillions of 'behaviors' (yepp, it has its own tech-lingo), there's even a modul which automatically animates based upon midi-data (if your source music comes as .midi files).
I try to teach it myself for quite a while - hours of frustrations, esp. when you're used to ready-made templates and 'boilerplate solution' with a single click.
I like to recommend the free, professional executed video tutorials from MacBreak Studio and Creative Cow, avail in the iTunes Podcast section - they offer an indepth look plus demo solutions for single tasks.- Have a look, wether that is within your … skills. Time consuming, but very satisfying in results!