As far as I can tell, there are two applications in the YAMAHA program group.

There's a 'hifi' program that can play MIDIs, WAVs, CD Tracks and has a mixer display showing the volume levels of the various inputs. No other options as far as I can tell.

There's also a 'ymersion' program that has a single checkbox that turns ymersion on and off.

edit - I forgot to check Control Panel...

The options are: Mic volume boost. ZV Port enable/disable. Softsynth configuration: Quality, Reverb, MPU401 out on/off.

edit - And there's a further page of options in the Drivers panel. Here's where the IRQ and DMA options are. Theres one option for irq and dma and they apply to WSS only. If I set any of these options, Windows asks to restart. It does edit the ini, but it doesn't have any options for disabling WSS.

I played around quite a bit with this card and also came to the conclusion that WSS can't be disabled. The card did however work very well...

I've received a replacement card of the same type which works perfectly!

The SB, FM and WSS test sounds all play in setupsa, and the settings save fine when the program exits. After you've set everything up, it politely asks if you want the setup to just print a message reporting the current IRQ and DMA of the different sound interfaces from this point on.

Compatibility:
The Incredible Machine 2, Waxworks, Mario's Game Gallery all working with SB sound and Adlib music.

Get Lost! sound config program runs with SB sound and Adlib music, but I can't get the game to run right now for some reason (this happens with no sound card, so it's probably nothing to do with this).

Tequila and Boom Boom works. It assumes Sound Blaster as far as I know and reads the BLASTER variable.

C&C RA autodetected it as a Microsoft Windows Sound Source, and it worked great.

Jungledyret Hugo works, and can set it as a WSS with Adlib music.

For some reason the Shareware Episode of DOOM doesn't like it. It causes the computer to reboot when I try to start the game with the music set as Adlib or Sound Blaster. With music set to something else like Gravis or Roland, it hangs on the 'initialising timers' line of the startup text. With music set to General Midi, I get no music but the game runs (this option is for use with the Game Port or wavetable connector, I believe?)

The card's FM sound seems tuneful and sonorous, if a little quiet in certain games. (Or blazingly loud in Waxworks.) Sound Blaster sound is, well, Sound Blaster sound. Hooray!

Are there any games with Ridiculously Awesome OPL sound that I should have a go of to test out my card now that it's working?

That's great news - is it the exact same card, the Audician 32?

Exact same card: "Yamaha Audician 32 Plus" ISA card with a Yamaha OPL YMF718-S chip, in the exact same box from the exact same person. 😀

Good to hear you got it to work! So it was the card after all...

Here's a long with technically impressive OPL music for you to try, you've probably seen it before here:
Technically impressive FM synth music

I personally like Tyrian, it has cool OPL2 music, and it's freeware.
Or you could install Adlib Tracker II and make your own chip tunes 😀

Some more games with WSS support that I know of include Dungeon Keeper, Carmageddon, and Redguard. There's also this analog synth emulator called AXS, it can use WSS for 16-bit 48KHz stereo sound in DOS.