Keep in mind, RAID1 (Mirrored) is just redundancy. If the file is corrupted on the 1st drive, it is instantly corrupted on the 2nd HD in the RAID1 configuration. Sometimes it's a fluke, other times it could be something like a bad sector on one of the HDs, in which case things can get botched up, as the data is mirrored. Keep an eye on things. Once...OK...things happen. But if you find multiple images giving you grief? Something is wrong with one of those HDs! Again, RAID allows for tolerance in keeping you up and running for as long as possible, so you can get to your data; RAID is not a backup strategy!!
How you choose to back up your data, is really a personal thing. In reality, before going nuts with backup strategies, it is more important to have a file/directory/folder structure that makes sense to you. This way you can avoid triplicates all over the place and you can find things quickly in the event of a disaster. Secondly, testing your backups is imperative. I can't tell you how many times I've performed resurrections and voodoo chants with my Customer's Servers, only to find out that several backup tapes are no good and they haven't had a good backup in MONTHS. Then their main HD dies and I can only restore the backup from 11 months ago, the recent stuff has to be inputted in, by hand, all over again.
So the first thing I would do, is to get your file structure files/folders straightened out, THEN purchase a larger external HD, like a 8TB (or even larger) to copy stuff to. One big data-dump. Use that as your "Workbench" to see how easy it is to navigate to, pretend your main HDs and Server was in a flood or fire. If you can figure out what is where within seconds, THEN you can pay attention to the Cloud Stuff and folders on your Server. Keep things simple. It doesn't do you any good not knowing what is and what isn't backed up when things go horribly wrong. Yes, this is going to be a PITA and a huge time-suck, but you are wasting time when things are working, rather than doing it the other way around, which is not fun at all. I speak from experience.
Offsite Backup is imperative, Home Server is another, and having external access to that server helps. Always remember, the Cloud is "Someone else's Computer," and OneDrive isn't fool-proof. In fact, NONE of them are and I would always remain skeptical of these services. TRUST NO ONE!! Always read the fine-print with Cloud Storage. I do not care how great a service claims to be, again...read the fine-print. That's why I recommend having a simple external HD to duplicate you main backups and then that EHD is stored off-site somewhere. For long-term storage, I recommend spinning traditional hard drives and not fancy SSD Drives for this. Why? Because Flash Media breaks down over time if the drive isn't powered on at least monthly. Digital Rot is a very real thing and a Traditional HD stores things magnetically, and lasts for years. SSD Drives? Notsomuch. Especially if you don't hook them up for a few years...the data goes "Poof."
So fiddle around with things. Figure out a Directory / Folder Tree. You need to be able to find something within 30 seconds at all times, that's the goal. In fact, it needs to be as logical as possible, in the event that someone else needs to find things if you aren't around to do it for them. Do a data dump to a large EHD, then see how easy it is to get to your files, even using another person's computer.