About "Windows Sonic for Headphones" and point "Does not work with games that auto-detect the speaker setup of the system." - doesn't the "turn on virtual 7.1 surround setup" in audio properties (where the Windows Sonic for Headphones and Dolby Atmos for Headphones sits) resolves this problem?
No. From my and other’s experiences, games still output in stereo mode if the speaker setup is set to 2-speaker (which it still is, even if "turn on virtual 7.1 surround setup" is checked). Checking the box only means that if fed a 7.1 (or 5.1, probably) signal, then Windows will downmix it to 2.0 using the headphones algorithm. Many games nowadays will determine how many speakers to mix for based upon the speaker configuration reported by Windows. Windows still reports 2 Speakers, so the game mixes for 2 Speakers and virtual surround is bypassed. This is why other solutions like Razor Surround are wrappers that pretend to be a 7.1 audio device, and output to an actual audio device.
Also, if virtual 7.1 is disabled but Spatial Sound is still enabled, then not much will happen unless the game has object support, such as Final Fantasy XV.
The easiest way to test for surround sound support in a game is using a virtual audio device that adds discrete 7.1 channels such as Razer Surround in conjunction with either Orban Loudness Meter or Special K.
Some things to note:
There aren't any game audio engines that require .sofa format instead of .mhr, but VLC does, so I'll plop this here in case anything else ends up needing them.