what's meaning of diffp/diffn/diffout matching like this ? is the diffout float ok ?
It is OK to leave diffp/diffn/diffout float when not using the remote sensing features.
Above arrangement is trying to disable the remote sensing op-amp inside the module.
if i don't use the remote sensing features. may i left all of diffp/diffn/diffout floating? or link them like the typical circuit ?
Yes. You can left them floating or link them as typical circuit show.
Got it and thanks