I have about 7 different laptops. One with Windows 10, an old MacBook Pro (circa 2012), a system with Linux as the primary, a Hackintosh clone (Mac OS running on a Leneovo X220), ... On top of that some of these are running virtualbox w/various guests.
I do local backups to external drives (when I do an initial set up and then occasionally). I also use OneDrive extensively for cloud based mirroring (note that isn't the same as backup).
I have three different OneDrive accounts:
1) A school provided one, which I use to hold all of my school related files. That way I can access things like saved grade books, instructors guides, etc from any of my laptops (or in fact from any system via the web interface). This allows up to 1 TB in data in the cloud.
2) A personal OneDrive account. Every once in a while Microsoft Office Home goes on sale for around $50 which includes up to 6 OneDrive 1 TB accounts. I use this for all of my personal data including pictures.
3) I have an "ebay acquired" business OneDrive account which allows up to 5 TB. Since there are some circumstances where the overall owner can access it, I use it exclusively for encrypted backups, including backups of my Personal OneDrive folders. I use Duplicati 2 (free) to do nightly incremental backups. This gives me some versioning on files.
4) For source files (programming), I use Git in conjunction with the above. So, I have local versioning and the source repository is incrementally backed up nightly.