My question, to Mcafee, would be about how it attained your address to apologize for a flawed download since you hadn't activated your subscription? It seems it was a "blind" mass/spam mailing taking a "guess" and seeking to entice people to its site/program.
I wouldn't be nervous; I betcha if someone checked the full pathway of the mail header, it might likely display that the mssg. you received didn't even originate from Mcafee. It strikes me as a guised method of "advertising."
About the best AV? I don't know if it's the best, yet I use Symantec Norton and couple that with running Bit Defender tools independently or as released. I prefer Norton over some others since I don't like the intrusiveness of some apps. - stopping everything instead of running seemingly seamlessly and silently in the background.
There isn't a single AV app. that is totally fail-proof. Each has an inherent failure rate - or misses (and its due to a lull between when newer virus codes are launched and when detection and definitions are updated). The miss rate is low, but... it's still a prob.
To greatly reduce the risks? Honestly? Mac 'puters

. PCs are more prone to attack/invasion/viruses because they are the object of malicious code-writers' affection/obsession.