I always used the Microsoft Security Essentials when I had Win 8. It was & seemed to run just fine. Never had viruses that I knew of.

Then, one night when the little update elves snuck in & unbeknownst to me updated me to Win10, I found that Microsoft had new free AV software called Defender. It seems to run seamlessly also.

I also use free Malwarebytes.

For backup, I use "Backblaze", which is not free for me. But, I sleep well at night.