I used to download two or three files at the same time. Then I changed the settings in NOD32 to a higher level of security, and found that now I can only download one file at a time. I find this disappointing. It must be possible to handle the usual two or three downloads at the same time, even when the scanner set-up includes all features incl. Advanced Heuristics.
In higher efficiency, IMON does not limit the number of files being downloaded at a time. I've seen a stack of IMON windows showing download progress of multiple files at a moment.
You might need to lower the limit for switching to active mode if you observe slowdown when loading web pages with tons of pictures, or set an exception for that website so that it's open in higher compatibility mode.