Your chances of contracting an infection are determined more by your browsing habits than by what protective systems you have installed on your machine.
So if you're someone who is cautious about what you click on, and has a reasonable level of scepticism. then Windows Security is going to be more than adequate protection for you.
If however you're the kind of person who feels they should be able to install a program that will protect you no matter how carelessly you peruse the internet, then I'm afraid you're in for a few nasty experiences, because truth is, there are no programs, or combination of programs, that are going to allow you to do that.
Adding extra programs usually does little more than duplicate protections already supplied by Windows Security, and though an alternate scanner may sometimes pick up things that Windows Security misses, they will not generally increase your security to any marked degree.
If you've gone 20 years without getting infected, I would guess that you are someone who falls into the first category, in which case Windows Security is all you really need.
I'm sure there will be others who disagree with me on this, and no doubt you will receive plenty of recommendations to "tie down" your browser by installing various extensions. But to be honest, most modern browsers have settings already built in, that will allow you to make them more restrictive if you wish.