First of all, it's amazing that you're considering all of this before a disaster strikes.
The major problem in your setup is lack of automated backups. Manually copying everything is not a long-term solution. As you've already discovered it feels like a chore. It's also prone to mistakes and you either have to keep only the most recent copy of all files, which doesn't give you proper protection against accidental modification or deletion, or to make full copies of everything, which is more time- and space-consuming.
Consider automating your backup. I'm using Veeam Agent to back up my Windows PC. You can set it to start automatically when you plug in a particular USB drive. It uses a proprietary storage format, which is a disadvantage, but this format lets it make incremental backups: only files that have changed are added to the backup repository and thus multiple versions of files are stored without duplicating unchanged files. Once in a while you can repeat a full backup, so that you can delete versions before it without breaking the repository (individual increments can't be deleted because following increments may rely on data inside them). Veeam Agent can also restore your system drive into a working state when it's too broken to boot. You just have to prepare a recovery USB beforehand. It's not a perfect solution, but it's good enough and the basic feature set is free.
Another alternative is Duplicati, which also uses a proprietary incremental backup repository, but lets you delete single increments. I didn't have much luck with it though - all backups were corrupted immediately after creation. The moral is that you should check if your backup is restorable before you need it.
We'll get back to backups in a while, but now let's talk about RAID. RAID offers you essentially only availability in case of hard disk failure. You seem to understand that it doesn't offer any protection against malware, mistakes and software errors. It also doesn't protect your drives from being fried by a faulty power supply or flooded in an unfortunate accident. The only benefit of RAID is that when a single drive dies, your files are still available and after replacing the drive loading data back on it is (maybe) a bit less of a hassle than restoring backups. Whether this matters for you or not is up to you. Anyway, you'd still need backups.
My last point is that NAS-es exist. They are self-contained little servers that you load up with drive(s) and they just do their job, sometimes offering some extra features. They are like USB drives, except they are connected to the network and designed to be always on. If you don't mind paying for the power to keep the drives spinning, they can be a great solution for main storage or for backups. For example higher-end Synology models like the DS220+ offer an integrated backup solution similar to Veeam's, but hosted and orchestrated from the NAS. These backups are also incremental, single increments can be deleted anytime, and you have an option to restore an unbootable system. Not to mention a ton of extra features (Dropbox-like file and photo sync, virtual machines, Docker...) and possibility to run RAID in these. (I promise I'm not selling this stuff, I just love them.) I don't think other NAS manufacturers offer any dedicated backup solutions, but you could use them for Veeam or any other backup solution over the network. QNAP has good reputation as a NAS manufacturer too.
