Am I missing something when the author writes about a free GCP instance with 8 vcpus & 64GB ram? Which one is that?

My second thought, why not scale that up to 64 vcpus (or even more) and spend less time rendering? I'm sure there's a balance between cost per second of render time and # vcpus. I haven't found it myself, mostly due to not experimenting.

When I render my product shots on GCP, I use a 96 vcpu instance and render relatively intensive (due to the higher quality of render and light settings) at print resolution in a minute or two. The cost becoming negligible, the feedback quick, and the strain on my MBP minimal.