you should leave the file anti-virus to recommended, setting it to low will scan infectable files by extension (so an exe renamed to txt for instance won't be scanned), while recommended scans the files by content (so that renamed exe will still be scanned). other then that the only difference is scanning ole embedded objects, which it's best to leave enabled, but you shouldn't worry the file av in avs should be fast because it has scan new and changed files enabled (of course that the file has to be scanned the first time) for the on demand scan you can leave it to recommended or set it to max, it shouldn't matter, the only difference is that max has parsing of email formats (treat email files on your disks like archives and break them to individual cmponents which are then scanned), enabled, but that's not a real security risk since an infected attachement will be detected when you try to run it