The article I've linked before contains instructions how to run some diagnostics.
Could you please post these (Task Manager showing CPU usage per logic core and GPU-Z showing GPU diagnostics parallel to Task Manager's CPU diagnostics while you play)?
Here is the photo. If you have any suggestions let me know.
What I can tell from this is that you don't have a dedicated GPU (just using the integrated graphics).
While this shouldn't be a problem on it's own, it can have implications:
I'd suggest a CPU cooler that pushes air toward the rear end of the case (toward the exhaust fans), e.g. the Cryorig H7.
Also, try if having a dedicated GPU solves the issue. You can just borrow one from a friend for a little testing, you don't need to commit to a purchase.