Quite topical as I've only recently properly thought about and improved my approach to how I deal with backups.
I use the OneDrive as my main source of file management, so I can access/sync between all of my devices (including my phone and my wife's phone, for camera upload). My two laptops are set to store the files locally as well, so they are on the devices, as well as the cloud. I then take regular backups of my entire OneDrive folder and put them on a 2 bay mirrored NAS, keeping as many as I can until I have to delete the oldest for a new backup to go on there. Every now and then (but not very often) I'll also take a completely offline/unconnected backup to an old external drive, mainly because I have a spare one laying around. Pretty much covers any (remotely feasible) scenario (component failure, device failure, losing a device, OneDrive gets hacked, house burns down). I guess without a properly disconnected/offline backup, a really sophisticated ransomware attack could (in theory) encrypt all of my drives, including the OneDrive and my NAS... but I'd potentially have a powered down laptop with a relatively recent version of the data in tact... but not very likely to happen, I suspect.
P.S. The reason I use OneDrive as my file management and my NAS for backups and not the other way around is because I want to be able to easily access my files from outside the house sometimes. And I trust Microsoft more when it comes to network security than I do the likes of Synology/QNAP and therefore don't want to (and do not) expose my NAS to the internet.
Oh, and all of my laptop drives, external drives and the NAS drives have full disk encryption activated. Mitigates laptop being stolen or home broken into and a device/drive being stolen.
A NAS box with mirrored drives in an alcove/annexed part of my lounge under the coffee table, along with UPS + router.
