You can turn macOS into Windows 3.1 reading a floppy by mounting an SMB share with a ton of small files and running an rclone sync between it and an external drive that has previously completed a sync. The stat() operations make the kernel go crazy. It’s the most appalling thing I’ve seen and has been broken like this since Catalina where it arrived as a massive performance regression.

You don’t even need networked storage for that, just attach a slow spiny disk and it’ll grind every app accessing the filesystem (even if those files are on a super fast internal SSD!) to a halt at random points.

Seems like there’s a lot of people with stuttering macOS https://apple.stackexchange.com/questions/245429/cursor-free...

USB-C and USB 3.0 devices are one common cause, Bluetooth mouse interference by USB another, and external monitors after sleep/wake another.

https://apple.stackexchange.com/questions/407177/windowserve... started happening in Big Sur to me.

I know this is random but my Bluetooth mouse was driving me absolutely nuts, and this workaround (which involves a GUI instead of running some random script off the internet) was an absolute lifesaver: https://apple.stackexchange.com/questions/377853/macos-catal...