Does anyone else arrange their data in a way that protects against the inevitability of a windows install failing??

No...I arrange it against the potential of the OS install failing. No OS is infallible or immune to you or some bad other thing happening. I wouldn't put my data on the same partition of a Linux install either- I wouldn't put it on the same disk even, if I could avoid it, just like on Windows. If for no other reason than historically, having all your stuff on the same disk as the OS could cause really significant performance impacts. It's less of an issue with solid state storage, but it's still there, to say nothing of storage density of hard disks vs solid state.

Plus, depending on what you are doing, it's very possible that your OS disk is the most active one in your system, so it's going to potentially have wear related problems much sooner than your data disks.

I see a lot of usb enclosures on Amazon but the idea of running like 5 disks over a single usb makes me nervous.

Why does it make you nervous?

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I also keep seeing the 4 bay qnap DAS that can do raid 5. That’s tempting too to prevent data loss.

The mantra: RAID is not backup. RAID is for uptime and recovery in hardware failure scenarios. Backup is your protection against data loss, not RAID. If your entire RAID array catches fire, gets struck by lightning, gets caught in a flood- whatever, if it hits the whole thing, it's gone.

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What would you recommend for external storage?

Well, you have to answer the "why" question above. There's no universal answer to this question. I myself on Windows, use multiple USB connected JBOD enclosures (16 disks). I use StableBit DrivePool to aggregate disks(on Linux, I'd use something like MergerFS), instead of any kind of RAID. I use a feature DrivePool has to duplicate specified folders across multiple disks for local redundancy to improve recovery time against corruption/hw failure etc to make up for not having RAID, with BackBlaze to perform backups to prevent data loss in disaster scenarios.

It works for me, and I'm fine with any differences in performance I might get- they largely just aren't that impactful most of the time in my use-case. It might not be what you want. You have to consider what things are most important to you to determine what storage setup you want to use.