If you have Lan1 and Lan2 set as 'Local networks' on the 'Global' tab, then traffic through them is examined by IPS.
If you list Lan1 as a 'Source Exclusion', then traffic originating in Lan1 won't be checked.
If you list Lan2 as a 'Destination Exclusion', then traffic to it won't be checked regardless of where it comes from. Listing Lan2 as a 'Destination Exclusion' is the same as leaving it out of 'Local networks' in the first place.
If you have Lan1 and Lan2 set as 'Local networks' on the 'Global' tab, then traffic through them is examined by IPS.
If you list Lan1 as a 'Source Exclusion', then traffic originating in Lan1 won't be checked.
If you list Lan2 as a 'Destination Exclusion', then traffic to it won't be checked regardless of where it comes from. Listing Lan2 as a 'Destination Exclusion' is the same as leaving it out of 'Local networks' in the first place.