I used Norton many years ago and it sure did become a beast, taking over the computer and slowing it down to the point where it was a pain to use! But that seems to be the way of all antivirus software now - something that was once good becomes bloated due, probably, to the greed of the developers.
In more recent years I have used AVG, and then Avast. Both started okay but with time they began slowing down practically everything I did with my PC, including even when not connected to the internet! And the boot times became sooooo long. As soon as the offending antivirus software was removed, all returned to a much speedier normal, so it was obvious where the problem lay!
Am currently using Avira. It seems to have a relatively small footprint and hasn't pissed me off ..... yet. I have been through the settings to try and ensure minimal regular intrusion, and the only pop-up that does occur regularly is the daily small window, soon after the desktop appears, giving me some startling statistic about the doom and gloom that might befall me if I don't pay for some other service of theirs. I just close it and am not bothered again until the next boot up. Seems a fairly small price to pay when measured against other ****e out there.
But who knows how long it will be before Avira builds itself up to be a ravenous, resource-devouring monster like so many others? By which time I will be looking again for something new.