RAID = Redundant Array of Individual/Independent/Inexpensive Drives.
The Redundant never was and never will be a backup. The Redundancy in RAID is for uptime in some RAID configurations.
All RAID is either Striped (RAID 0) or Mirrored (RAID 1). All RAID variations are based on this.
Striped RAID (RAID 0) is where data is written/read simultaneously written/read from two or more drives, increasing throughput. The necessity for this has been largely negated by SSDs.
If one drive in RAID 0 fails, you lose whatever was on that drive(s).
Mirror RAID (RAID 1) mirrors the data across two for more drives. What happens on one drive(s), happens immediately to the second set of drives. Accidental file deletion, overwrite, corruption, accidental format, happens to the mirror drive(s).
If you lose the mirror drive(s), it's possible, but not guaranteed you'll be able to fully rebuild the array.
If anything physical happens to any RAID setup; fire, flood, hurricane/tornado, power surge, theft, happens immediately to everything in that setup. THIS IS WHY RAID NEVER WAS AND NEVER WILL BE A BACKUP!
Backups are physically detached storage, ideally at least wo sets, with one offsite in case of a local catastrophe.
There are RAID configurations that use additional drives or parts of drives for parity that allow you to potentially restore lost or corrupted files. But again, does nothing for a local catastrophe. Only proper backups, probably the one offsite can do that.
From your description of what you want, you want DAS = Direct Attached Storage. DAS can be individual external drives (as you have) or combined into an enclosure. The $600+ enclosures you're looking at are NAS (Network Attached Storage, usually with RAID capability) Almost all NAS* have to connected either physically through an ethernet cable or wireless.
A NAS, with or without RAID is expensive because it's essentially a computer without a monitor.
*Some routers allow you connect a drive via USB, that in turn becomes a NAS, available to the other devices on your local network.
The best fit for your need is a DAS (Direct Attached Storage) without RAID. A DAS can be connected via USB or eSATA. 8 bay DAS enclosures like this SYBA, start at just over $200 https://www.amazon.com/Syba-Swappable-Drive-External-Enclosure/dp/B07MD2LNYX
Where a NAS is smart, a DAS is dumb. It's the same as an external drive with the multiple drives going through a single USB or eSATA connection. Since you're using hard drives without RAID, a USB 3.0 interface is more than enough. Don't pay extra for USB 3.2 or USB-C.
Some will say "If you have more than XXTB of storage, you NEED A NAS and or RAID!". Nope. If you don't need the network accessibility, a DAS of any size if fine. I have 200TB in DAS. Two 8 bay and one 4 bay enclosure. All separate drives.
Which brings us why I don't use or recommend a NAS or RAID.
Because of it's connectivity, a NAS leaves permanent links to it's existence when turned off. This opens the door for viruses and ransomware from device with access to your NAS to attack your NAS and any other device.
When a DAS is turned off, it's invisible. Just as any other external direct attached device. This is also why my main setup isn't connected to the internet. Much harder to attack what can't be seen.
I don't use RAID because I make proper backups, two sets* of everything I have. I have a very specific categorization system and like being able to replace any failed drive at any time with virtually zero downtime since I also have spare drives to immediately replace my backup drive(s).
*Unfortunately, I have both at home. I have nowhere physical to keep the drives and cloud would be to expensive. But this is do as I say, not as I do, because I have a love/hate, growing to more hate everyday (which I've talked about in my other posts) and will shed no tears if/when everything disappears.
There are drive bays like this.
I have this one and can't be happier. https://www.amazon.com/dp/B07MD2LNYX
Sorry I just read where you said it will not run on 240v. I checked the q&a on the page and I thought it said it would.
https://www.amazon.com/gp/aw/d/B07MD2LNYX
very happy with it. i have 4x of these, used for my backups