Both those detailed studies are fairly easy imo. I found Electronics and Photonics the hardest in Unit 3 and probably Interactions of Light and Matter was the hardest in Unit 4. For me, I found VCE physics to be far more boring than hard though.
Yeah I kind of wish I did UMEP physics... 
What SS did you get for Physics?
Haha, I fluked a 41 raw

Barely any study (literally crammed it the night before and morning before mostly), definitely didn't deserve my score. I also don't recommend taking my approach!
I just hated physics, I found every topic to be extremely dry (and my terrible teachers didn't help either) and I lost motivation early into Semester 1 (April-ish I think?). We played CS every second physics lesson, and my class didn't so well in physics, despite arguably being the strongest MHS class by a very long way.