Your first gripe kind of sounds like DLP software is installed on the system and it is scanning files you're "accessing".

I don't know, my personal windows install which I use for photoshop, lightroom, and the occasional game also has similar issues, and it only has the included windows defender. I've noticed on many computers that whenever there are a bunch of files in a directory, the explorer grinds to a halt.

At work we use clownstrike for our driving-around-with-the-handbrake-on needs, which I have installed on both Linux and Windows, and the former flies while the latter lags all the time (I dual boot, so it's the same exact hardware). Doing something which is fully equivalent, like installing an IntelliJ update takes around a minute on Linux and many more on Windows.

The fan also comes on much more often on Windows than Linux, even though most of my job is done on remote servers via SSH. Under Linux I only hear the fan when I compile something. This morning I booted windows and the fan was running constantly while I was just catching up with a few mails in outlook.

If it's DLP then using alternative file browsers should also be affected, right? Which at least in my case it isn't.

On my company provided laptop with Windows 11 (previously Windows 10), the top three CPU usage was and is usually from Antimalware Executable, Microsoft Defender and MS Teams (or Crowdstrike). I don’t download files or get files from other sources often, yet these things keep doing busywork and slowing things down. Despite virus and threat protection running quick scans often and forcing a full disk scan every couple of weeks or so.

It’s almost as if these programs are people who ought to show that they’re doing something even though they’re just heating the room and running the fan.