what settings to pick when converting flac to alac with foobar to get the cleanest conversion?

[Jerrod]

should i just put the output bit depth in auto?

dither always or never?

should i pick any dsps?

Anything from the "other" section?

 

[GREQ]

You're converting from one lossless format to another lossless format, so by design it should ignore things like dither and bit depth anyway.
Otherwise it would not be a true lossless conversion.
I'm a little concerned that the developers didn't grey out these options while a lossless format is selected ... that's just bad user interface design.

In the worst case, turn off dither, and chose the same bit depth as the source material.

Never pick any DSP - this will contaminate the fidelity of the 'lossless' conversion.

With that I think you're good to go.