First, might I presume "in parallel" might mean "running a virtual machine in Parallels"? If so, that is not light usage. Nor are most virus scans, which involve deep inspection of many thousands of files. Neither usage is typically throttled to reduce CPU or power consumption. Depending on your virtual machine setting in Parallels, it could even be consuming all your cores, especially if you're running more than one VM. Both these usages will spin up your fans, sometimes a lot. You might try a different virus scanner; maybe you'll find one that isn't as eager to press the pedal to the metal. macOS doesn't need frequent virus scanning anyway (though a Windows VM will). Activity Monitor and its equivalents in your VMs might tell you a thing or two also. For example, I had a hung driver in a Windows VM a few months ago that was spinning up two cores and killing my old machine's performance and battery life and, yes, making it run quite hot. I have a similar machine, six-core i9, top spec, lots of RAM, and sometimes when I really pound it with more than one VM it'll get somewhat warm, but never hot. It seems to run much cooler than my dearly departed 2014 rMBP that it replaced. I hope you get this sorted and end up as fond of your new machine as I am of mine!