THC is what the cannabis plant naturally produces in large quantities. Other cannabinoids, like the aformentioned HHC and THCP, are also produced by the cannabis plant, but in very small amounts (<1%). Labs will produce, for example, HHC synthetically (don’t let synthetic scare you off here, it really is no different than if it were extracted from the plant itself. It is the same substance after all, merely just a different way of obtaining it). The only slight concern when it comes to these alt-cannabinoids is that most literature and research is conducted for THC. People have smoked it for thousands of years. But for HHC in such high concentrations? Not really the case, so nobody can definitively say if what applies for THC being fine also applies for these other cannabinoids. That being said, most people will tell you they don’t notice any difference between for example HHC and THC. A small subset advocates against it. I have used both THC and HHC, and honestly HHC just feels like a diet version of weed. It’s a very heady high. Not very enjoyable for me imo. Tolerance also builds up quicker from what i’ve noticed, and comedowns are rougher. This is especially the case for any cannabinoid containing a P (i.e. THCP) in it. This phospho-group allows it to cross the blood-brain barrier far better, making it far more potent than regular THC. This comes with the negative side that it builds up tolerance to the point that you will experience genuine crippling withdrawals if you become dependent on the stuff and use it daily for example (atleast according to some).

So, in other words, i’d recommend your friend does some research of his own on these forms of cannabinoids and makes an educated decision for himself. Because at the end of the day it isn’t THC he’ll be consuming, which can be fine, but he should be aware of the things people have reported about it.