Ideally, Output Format should be unchecked, but if you're still getting the little blue indicator for Audio Path (indicating no changes are being made) then you're OK.

You might take a peek in Output Format settings. Make sure Bitdepth is set to Source bitdepth and Channels is set to Source number of channels. Otherwise, keep Output Format unchecked unless you run into an error message where you have to force playback to a certain bitdepth for compatibility.