I also only use free versions of Avast, MBAM, and Spybot along with script blockers like AdBlockplus, Ghostery and uBlock origin. I used to use avg but the Avast has been real good at blocking malware in real time.
The only thing I pay for is my VPN which is cheap and can cover up to 7 devices. The odd time I'll do a scan with Zemana as well but don't have it running.
If I ever have a feeling that something seems funny my go to just in case is a system restore which has never failed me.
Personally I would never use Norton as it's always been known to be a resource hog using way too much CPU and memory.