How do I remove the extra stuff they have apparently recently added to the "volume overlay" pop-up thing in Windows 10?

Solution 1:

Microsoft has included media controls in the Windows 10 volume overlay as an option for application developers to take advantage of for quite some time now, and it isn't a new feature in Windows 10 version 2004. Unfortunately, I do not think there is a way to disable the overlay system-wide. It is entirely up to the developer of an application whether or not to include integration with Windows' universal media controls.

That said, foobar2000 enabled integration with Windows 10's Universal Volume Control by default in version 1.5.1 (changelog here). You should be able to disable it by going to the Preferences menu, then clicking on the "Advanced" area (at the bottom). Under "Display", find a checkbox with the text "Integrate with Windows 10 Universal Volume Control". Uncheck if it is checked, and it should disable the "feature".