Disclaimer: 25 years in I.T. (programmer > project management > system design) and more than a little paranoid...
I run a minimum 3-2-1 backup strategy for my core backups: 3 backups, 2 different media types, 1 offsite.
In addition, while I'm working on story, I do incremental backups to a dedicated USB drive whenever I'm going to be away from my computer for more than a couple of hours.
None of my backups use devices that are not mine, nor do I use backup software - you cannot guarantee access to the former, and it's just another software layer between you and your files with the latter. I also classify email as 'devices that are not mine' and thus never use it for backups.
I regularly check my backups, and bring older proprietary files to compatible versions wherever possible, or switch them to plain text/basic .jpeg images.
All offsite backups are encrypted using high grade (industrial level, not military) software that I own lifetime rights to, and all encrypted backups have an installer image of the encryption software (package, no keys) somewhere on the same device.
Finally, I never use authoring packages. Word, Excel, and Notepad are it.
Keep it simple. Do it regularly.
The last time a computer died unrecoverably on me and I had to rebuild from the ground up, I only lost twenty hours email. Since then, I've switched email strategies so that loss will never occur (unless someone nukes three countries across two continents - if that happens, I have bigger problems than retrieving my emails. )