In the end, I decided that the automations made me a little nervous, and I instead created shortcuts that I just try to remember to run manually. Putting these on the home screen or in the dock on my iPad help me. It’s possible to call these shortcuts from whatever automations you like on whichever device, once added.
I also dramatically simplified the actions in those shortcuts after I learned a bit more about what I’m doing. Below, you can see links to add these shortcuts:
As for why automations made me nervous—or more to the point, to answer your question about whether I’ve had any issues so far—the primary issue is that I don’t know how to forcibly trigger iCloud Drive to sync before firing a shortcut or automation. In my experience, it works fine. But it gave me a little more peace of mind to make sure that I could check the files myself before doing the copying, and I did not find this manual process (look at files, hit a button) to be untowardly burdensome.
I see there’s some really interesting discussion elsewhere on the thread, so I’ll follow up on that in another reply.