I think you can get back to Win9x/2k style controls by instructing the system to not add any theming. If you're finding a panel that is using 3.x controls, they're likely in the resources of the app/dll. Although the 3.x file picker can still be found in a couple of rare corners of the OS.

https://learn.microsoft.com/en-us/windows/win32/api/uxtheme/...

    STAP_ALLOW_NONCLIENT

Specifies that the nonclient areas of application windows will have visual styles applied.