[melons2]

When you go Settings > System > Audio output:
There is the setting:

Output configuration

[Fixed] - output properties are set to the specified sampling rate & speaker configuration at all times
[Optimized] - output properties are set at the start of playback and will not change if the properties of the source changes
[Best Match] - output properties are set to always be as close a match to the source properties as possible

I have a networked Lenovo Q190 > HDMI to a Pioneer Elite sc-57
set to hdmi waspi
and passthru enabled

which of the three choices above would be best for me?

[Atreyu]

That's something you should decide for yourself.
Descriptions leave little to guess...

But i'll give you my choice and why.
I choose to have sound fixed at a certain rate, because the changing of these preferences causes a short clicking sound in my particular setup.
Why not just try the different settings and see which you like best?

/edit I just noticed you have enabled passthrough.
I font think it matters what audio output settings you set as sound it literally passed through as-is (somebody correct me if I am wrong here)