You're right, the Force is inconsistent and it's also plot dictated. That being said, a big deal was made about Force sensitive people getting the proper training and even TLJ acknowledges this somewhat, perhaps just to subvert it.
Your description of Snoke reminds me of Palpatine in ROTJ. He didn't have a lightsaber, or at least a visible one, yet he radiated power.
Ren has been inconsistently portrayed. I don't think it's an issue of overrating him. I mean he caught a blaster bolt in mid-air, that's pretty powerful. He has been portrayed as powerful, yet unstable from jump. If I recall, in TFA it mentioned he murdered several of Luke's students and we see in TLJ the result of his handiwork, destroying the Jedi Temple. We also saw him do a force choke with more power than any Vader has administered when he checked Hux. And to his credit, he had taken a shot in the side before he fought Finn, and he possibly was toying with Finn somewhat-being a sadistic jerk-before getting to Rey in TFA. We don't know if the Praetorians were 'normal' humans. And it's likely we won't find on in a film, but possibly from one of the books or comics in the future.