Paranoia may just be a healthy fear of the unknown. This may be a problem you can solve long-term, with a second computer, some reading, and a better understanding of how to weigh risks, care for the security of a PC, and wind up with a better sense of security overall. I have some suggestions that helped me along my security journey.
This is an older book, but the principles still apply, and it explains the proper way to think about Security without bogging you down with details; focusing on what matters. It is geared toward businesses and organizations, but it is the book I'd recommend to anyone who wants to understand the Windows security model and how it works. It is excellent on concepts, but again, it is older.
Protect Your Windows Network: From Perimeter to Data
https://www.amazon.com/Protect-Your-Windows-Network-Perimeter/dp/0321336437
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There is also an architectual reference guide if you ever want to look up X on Windows. Here is the latest edition. It can help if you ever wonder what a thing is in Windows, but this is HIGH end, and you have to have a certain level of understanding to understand what you are reading.
Windows Internals 8 Developer Reference
https://www.amazon.com/Windows-Development-Internals-Developer-Reference-ebook/dp/B00JDMPL8M/ref=sr_1_1?crid=37SIMV89C057C&keywords=windows+internals+8&qid=1662050977&s=books&sprefix=windows+internals+8%2Cstripbooks%2C96&sr=1-1
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On the edge of the beginner level, free for Kindle Unlimited, Windows 11 for Beginners 2022: The Most Updated All-in-One Guide to Master All the Features of your PC and Make it Faster and Protected | Learn how Operate with Windows 11 in 7 Days or Less My guess is that this material is probably things you already know. I've included it here for completeness. That being said, I've been doing this professionally more than 20 years, and I still learn new, simple tricks from folks all the time.
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Finally, when things go wrong...Sysinternals is Microsoft's troubleshooting toolkit. They have a guide.
<strong>SYSINTERNALS.COM</strong> Powerful tools. Lots of them. Written by the same folks who wrote Windows Internals.
I SAID ALL THAT TO SAY THIS
You don't sound paranoid. You sound like you are trying to figure things out. There are places to read about it and find out. Snatch up some books, or a kindle edition because a lot of this is on Unlimited and it is free. Get a tiny low-end PC you can play with, and never put any personal information on, and test (carefully), and play (carefully), and learn (always). You'll get more comfortable.
It's a little dated, but an excellent read.
https://www.amazon.com/Protect-Your-Windows-Network-Perimeter/dp/0321336437/ref=sr_1_1?dchild=1&keywords=from+network+to+perimeter&qid=1624399809&sr=8-1
Protect Your Windows Network: From Perimeter to Data
"In some ways I consider this book to the be Windows counterpart for the Unix security book listed above (Practical Unix & Internet Security, 3rd Edition). However, this book also features deep truths that apply to any operating system or enterprise."