Just like any other SW, AVs should be balanced between computer "power", system and security needs. If one has need for enhanced or extreme protection, than computer itself has to match that requirement but also to be ready to "suffer" with it's drawbacks. With increasing threats, comes increased need for protection and that of course can tax system. Some of that can be alleviated by being careful and informed. Perfect balance is pretty difficult to achieve.
Using something like Macrium Reflect to image one's OS is a good idea.
I think you should try F-Prot. That is what I use and it works great and does not hog system resources. you never know its there until you need it. The way an Anti Virus program should be.
I always recommend GData Internet Security. Has never let me down so far and it's generally trouble free. Ok, no software has no bugs at all but this one is very well designed according to my experiences.
Windows Defender and MalwareBytes are all I use...