Remove all custom fonts?

I have a lot of fonts, more than 10,000 to be exact, it is slowing down Photoshop quite a bit. I was told to remove all custom fonts and then install a font manager. However, I cannot figure out how to remove the custom fonts. Google and many other websites tell me to do this.

1. Go to Control Panel -> Appearance and Personalization -> Fonts.
2. In the left pane, select Font settings.
3. In the next window click the Restore default font settings button.

But that is incorrect, that only restores the default fonts like if a default font is missing or corrupt. It doesn't remove any custom fonts. I don't see any working tutorial on the internet on how to remove custom fonts. Just the one I posted that doesn't work. I don't understand why removing custom fonts is so difficult. Can anybody tell me a working way to remove all custom fonts. The only one I find anywhere, is the same one, which doesn't work.

How do I be sure I don't delete any fonts the OS needs or other software needs?