(1) Best backup your important user files & raw downloads to external media. I'm sure it says so in that TenForums article even though a repair-install should keep them (as well as apps). Also, I'd put them on OneDrive (if they will fit) where they also should be safe even after a clean install (if that proves necessary). But a clean install does wipe apps which would need to be reinstalled. I see you have Office 16 installed. Do you know how to reactivate it? You'd have to do so after a clean install.
(2) Your Reliability History & Event Viewer look horrid. I'm leaning against trying to investigate & fix your critical errors. But to do so in the former, you'd click those View Technical Details buttons to see what is crashing. Do so for the various days you've got a red X. If it's mainly one cause for all of them, we might try solving it.
In the latter, you'd open to the Event Viewer (Local) page, double-click Critical to open it, then double-click the items under it to see what is said. I thankfully have none that are critical these days. The arrows at top left are helpful to navigate.
(3) Did 21H1 come in through Windows Update? What was the prior version of Windows that it updated? If it was lesser than 2004, then it didn't simply turn on switches but it was a full upgrade that will be uninstallable at "START, Settings, Update & Security, Recovery, Get Started (under "Go back...)",,,
That worked real quick & well for me once for a different problem. Afterwards, I would try the upgrade one more time to see whether it will install better.