Sith are a fictional sect of religious space wizards from a space opera. While they may have inspiration from religious sects of reality, they are very much not real. So, whether or not they deal in absolutes has absolutely no consequences to reality outside of the Star Wars fandom.
I maintained a CEPH cluster a few years back. I can verify that speeds under 10GbE will cause a lot of weird issues. Ideally, you’ll even want a dedicated 10GbE purely for CEPH to do its automatic maintenance stuff and not impact storage clients.
The PGs is a separate issue. Each PG is like a disk partition. There’s some funky math and guidelines to calculate the ideal number for each pool, based upon disks, OSDs, capacity, replicas, etc. Basically, more PGs means that there are more (but smaller) places for CEPH to store data. This means that balancing over a larger number of nodes and drives is easier. It also means that there’s more metadata to track. So, really, it’s a bit of a balancing act.