the delay aspect is a little more delicate than what you describe and the cases are often very variable...
( in any case this immense variability in the acoustic conditions will necessarily make the exchanges difficult and relevant in the discussions on the correction..)
Absolutely no delay should be applied to a stereo pair of speakers, unless you’ve placed furniture inbetween the driver and your ear. I’m presuming a listening position in the middle, as it should be.
The direct sound from the two speaker will reach your ears at the same time, delay should be set to zero, unless you live in a magic room where pixies make the air pressure higher at one side of the room than the other.
Now it’s possible some reflected sound will be delayed to one speaker and not the other. Let’s say your right channel’s first reflection requires a delay of 2ms.
Great. Enter a delay of 2ms. But hold on, you can’t just do that for the first reflection, the direct sound will be delayed, too.
You’ve now made the louder, more prominent, direct sound from the driver, which was perfect at zero, imperfect by 2ms, to correct the quieter, less important second reflection.
That makes no sense whatsoever.
Bottom line, if you have a 2.1 set up, and all 3 speakers are the same distance from you, then the correct delay setting for each one is zero.
It’s only when you bring in multiple seats, more speakers, and less control over furnishings in relation to those speakers and seats, that delay becomes an issue.
Sorry, to be accurate, there is one caveat. If processing is involved this
can introduce delay. However, as all processing is being done by the WiiM in this instance, we can discard that caveat in this scenario, unless your sub has its own built in dsp. And if it has, guess what. You can control that from the sub’s app.