I recommend ** outpost firewall** since it alerts you when software makes changes to your files and lets you see indepth whats running in the background. since it's not scanning every file for integrity and instead protects them from being changed in the first place the resource usage is alot lower. you just need to use malewarebytes after you install a new program so you know your pc is safe before you allow it to do somthing.
another nice thing about it is that it can be used as a system wide adblock. it can even block windows update if you need it to.