Doesn't spook.js also rely on the user installing a specific browser extension? Yes, I suppose it does use spectre, but if you control a compromised extension the user has installed, you could steal more data faster without using spectre.
My bad, I thought Windows Defender was the firewall. ChatGPT tells me it's actually a service that hashes executables and checks them against a table, like an old-fashioned antivirus, so I guess that would be a much higher impact on performance. Still, I'm sure I've seen "disable your firewall" on various "how to install game" and "game doesn't run, pls help" pages.
If you want info from someone who knows something about Windows and not a glorified chat bot, Windows Defender and Windows Firewall are two separate things. Windows Firewall existed for a long time and it's meant for filtering what network traffic goes to which parts of the system, while Windows Defender is basically Microsoft's antivirus that comes pre-installed with Windows.
For example, Windows Firewall was first introduced in Windows XP, but in those days you had to install an antivirus separately. Microsoft's offering was Microsoft Security Essentials, which got remade into Windows Defender and made a part of the OS by the release of Windows 8. And yes, sometimes Windows Defender hogs your CPU and RAM quite a bit when doing it's thing, so it does have a much greater performance impact than the Windows Firewall which is only meant to do simple network filtering.
So no, those are two independent parts of the OS, with the firewall component being much older than Defender, which is an iteration of Microsoft's older antivirus that's bundled with the OS since Windows 8.
EDIT: As for Windows UAC is, basically back in the days of XP any process was ran with admin privileges, meaning that you could very easily run a malicious piece of software that would fuck your entire computer up because there was no distinction on what a given process can do. By the time Windows Vista rolled out, Microsoft introduced UAC, which basically introduced a restricted access mode for processes. So if a process doesn't need full admin access, it won't ask for it, but if it does you will get the UAC prompt asking if you're sure you want to give it admin access.
It also introduced .exe signing, meaning that if it was, let's say a Google Chrome installer, it will show you that it's not signed by Google, meaning it was most likely tampered with and you shouldn't install it. Of course, if you try and run something older than that, let's say an older game, it won't have a signed .exe and it will require admin access to run properly because that's how some games were designed back then. It all boils down to you having common sense of when to be suspicious when a UAC prompt pops up.