https://www.cnet.com/news/best-gaming-pcs-for-2019/

It's all about tradeoffs. Every game uses system resources -- processor (CPU), graphics processor (GPU), memory (RAM), storage --  differently, and often horribly inefficiently. You can't even count on resource usage consistency across a specific game genre, such as first-person shooter (FPS) or platformer, because optimization levels can vary wildly. Gaming (and content-creation) PCs are the angry toddlers of consumer electronics: they are loud, willful, require constant supervision and just when you think they're under control, they veer off into crazytown. 

I'll admit, I'm waving my hands a bit here: these are not recommendations for specific systems, more for ballpark configurations and suggestions of the manufacturers or system builders with a specific case design that you should consider in various scenarios. (And when it's time to sweat the details, User Benchmark is a great site for getting a sense of performance deltas between different components.)