You can exclude asset types from scanning in the Assettype Exclusions section of Configuration\Scanning Methods. It would be better to have the Mac computers correctly scanned though. If you scan the Mac computers as documented
here, they should be correctly identified.
Moving network interfaces between non-Windows assets can cause scanning issues, mostly scanning failures of the asset the interface was originally connected to. This is because all of a non-Windows asset's MAC addresses are expected to be unique. You could blacklist the affected interface to prevent these issues however, by adding it to the tsysmacblacklist database table.