You don't need either one, but between the two a VPN certainly isn't going to help protect your Mac from anything. Don't use it.
If you want to be vigilant protecting your Mac, then read Effective defenses against malware and other threats - Apple Community. Various programs claiming to do that on your behalf tend to fail miserably at the task. Delegating computing security to an app is irresponsible, no matter how "recommended" or "trusted" those apps may be.
For reasons that elude rational explanation various commercial VPNs seem to have become popular. They make dubious claims that don't stand up to scrutiny.
The only legitimate purpose of a VPN is to provide a connection to a private network — by definition, one that is not connected to the Internet and cannot be accessed any other way. Commercial VPNs that serve to forward your communications to and from publicly available Internet sites cannot possibly convey any greater security, and only make data-harvesting and general eavesdropping on your Internet activity easier for those with nefarious intent.