Windows defender is all you need, but the most important thing is to not rely on the antivirus in the first place, it can't protect you against zero-day malware and other threats, so you should just learn to never install untrusted software, and if you do need to do this, then do this in a separate environment - i.e. get a dedicated computer for pirating software and games, and another for your work, finance, personal stuff.
People often recommend Linux, but I don't believe its a silver bullet, unless we talk about something like Qubes OS - you'd still better have different environments for potentially risky and sensitive stuff, even if both run on Linux.
Windows 10 collects your data, it is one of the reasons of its existence (vs the older versions). Microsoft knows every single file name you have, they can also retrieve them (download) if they feel compelled to. I believe they also get the generated thumbnails, there is documentation on the bucket load of info Microsoft themselves collect from you on various sites online.
Linux is far safer by default than Windows ever will, its probably in their model anyway to be easy to break for various reasons (and their separate department development model leaves no choice). And that is before you start adding software, which will simply diversify the number of companies that get your private data.
Datamining is exactly what Microsoft wanted to get into with Windows 10, there is no coincidence Windows 10 increased that data collecting following the trend of similar Google products.
With Free and Open Source software like Linux you have the code and can audit it yourself, or pay others to do so. Are you scared of spying? Check the code, compile it yourself; invite others to do their independent reviews, report anything you find.
Your mentioning of Quebes seem to be ignoring the recent security flaws of speculative execution in most modern CPUs; virtualization is NOT a silver bullet. If you want a "safer" system then get something like the Pinebook pro or some architecture without these flaws.
In Windows installing from untrusted sources is "normal", people are used to find things in web pages, download and install, as opposed to using an official repository like most Linux distros have been doing for decades. You would need to break couple of decades culture of bad habits from windows users, such as running with administrator privileges. And even if they were disciplined to run as a limited user, they will happily execute dubious programs downloaded or brought in that can escalate with or without permission anyway. That's how the infamous Stuxnet invaded an air-gaped facility in Iran, the idiots were using Windows scada terminals and some bored operator probably wanted to play games or see pictures on his usb stick to pass the time...
Yes today Avast made the news, Avast is not the only one, most windows programs do this including windows itself. This is also true of closed source proprietary apps, you could attempt to sniff your network but many do this encrypted to "normal looking" sites.
Without the source code, you can never tell for sure your program or operating system isn't doing something behind your back. You simply can do nothing buy blindly trust in them, like you would trust your government will never ruin the fiat coin of your country.
It makes a GIGANTIC ton difference to use Linux vs Windows, even at default settings. I don't care if you replace Linux with similar FOSS OS such as Freebsd, or Windows with similarly closed proprietary software such as OSX. The same goes to all user programs. Do not excuse laziness over learning "something not Windows" by justifying yourself with "any 2$ chip can sniff you anyway so why bother"? If we bring here every possible single vector of attack, we would never end. The point is to reduce them, not increase them. You increase them many fold by telling people to not bother with Linux. Yes it matters, yes it makes a difference.
To anyone reading this still on Windows: Linux is free and open source, try it. Nobody is forcing you a subscription or referral program. There are
thousands of distros you can try, test as many as you want until you find one that you like. Many can be tried without installing, you can even disconnect your hard drive if you are scared to accidentally lose your data, just let it boot from the usb stick or optical disc.
See for yourself, make the difference and tell others. Linux is to Windows what Bitcoin is to Ripple.
