Been thinking on this. It is a great question.
Document/file naming conventions. I still use year_month_day_file_name.
As a senior, I too am concerned as to how my clean up crew will be able to access my digital documentation after I am gone. They SURE DON’T need to be experts at a specialized app.
Universal file extensions, that LAST through time, (like .txt). And not only documents, but video too. (I have several old videos of my kids, that I can no longer play 
).
WHERE and HOW to do long term digital storage, so that not only can it be accessed by my device, but again, my clean up crew when I am gone.
Is there a way, using iCloud or Dropbox, to store my files on device, AND in the cloud, AND they not automatically delete/overwrite the other.
A side note:
I live in hurricane land. Having my “stuff” in digital format, AND accessible when there is no internet is a MUST. The days of carrying a plastic tote with your important documents in it is about gone. Most shelters don’t like them. Security.