PC Gaming Surround Sound Round-up (satsun.org) - Last updated 12 December 2020, XAudio2 can passthrough DirectSound (emu as you said) or WASAPI.
"WASAPI, DirectSound and MME interfaces can be considered "high-level" only in comparison to Kernel Streaming because they are built on top of KS. In modern
Windows versions, these interfaces are often considered "low-level" because higher-level ones (
AudioGraph,
MediaCapture,
MediaElement,
XAudio2) are offered. Meanwhile,
XAudio2 is often called "low-level" because it offers hardware-close streaming control."
"
WASAPI interface has been introduced in
Vista. The abbreviation stands for Windows Audio Session
API. It supports both
shared and exclusive access modes. In the
exclusive mode, it is highly efficient like hardware-accelerated DirectSound, but in
shared mode, its efficiency is comparable with shared-mode MME and DirectSound (not accelerated)."