Does Windows NT have a Windows 9x API emulator?

Windows NT predates Windows 95 for two years.

And yes it did had emulators for Windows 16, and DOS

https://en.wikipedia.org/wiki/Virtual_DOS_machine

https://en.wikipedia.org/wiki/Windows_on_Windows

If you squint a bit (well, a lot really), Win32S on 3.1 and Windows 95’s Win32 implementation are Windows NT emulators running on top of 16 bit Windows.