It's not that simple, because it all depends on the configuration of the computer and which AV program we use. I have 8 GB of RAM and a pretty powerful AMD processor, and I don't feel like I have Norton Security and Malwarebytes Premium in the sense that they overload the system. Norton actually consumes just over 100 MB of RAM, while MB spends twice as much, but considering the total RAM, the work on the computer is without any difficulties.
I think we should dispel the myths that were created 20 years ago when computers were actually like toys compared to today, and that no modern computer with a solid configuration will have problems with security software. However, it should be emphasized that there are big differences between AVs, and free ones should definitely be avoided because it is obvious that they charge for their service in some other way.
In my case - i7, 12GB RAM - I do get annoyed by the Auto Containment feature that sometimes doesn't recognize an installer, some other time doesn't recognize an exe built by myself, or some other time doesn't allow me install an update to one or another wallet. Or I feel how the antivirus slows me down when I backup folders with 10000s of files.
Of course, I don't use such a computer only for browsing the internet...