I gotta say, this is the first I have ever heard of ScanGuard, which means pretty much nothing other than I never heard of it.
Researching it now, it seems well reviewed. Do you need it or should “no Mac user be without it?” Personally I would say that’s marketing hype and I am definitely one Mac user that plans to be without it. But that’s just me
About the only thing most folks should consider is a tool that helps with adware/malware. Some modern AV does that too...but as Malware Bytes is free and arguably the best, not much need for more.
Unless you are in an environment that requires AV, then there are options to consider. If AV is required: Sophos Home, free Avira, and free Avast seem decent. The free version of AVG seems pretty good, but it is nagware.