It’s very hard to see in that latest screenshot but is it showing your GPU utilization at 96%? If that is the case, then you might just be limited by your CPU main thread performance now.
I have heard that flying “closer” to things puts more of a strain on your CPU, because the engine must start calculating more collision models. It needs to know where the borders of all the trees, buildings, etc… are to determine when you crash into them 
As you have a laptop CPU (even though it’s a pretty strong one for a laptop), it’s possible you’re just hitting CPU single thread limits. Things to try - turning down your TLOD slider, turning down traffic settings (or turn them off for test purposes).
Good luck.