Had the XPS 9570 for a half a year, the thermal throttle on it is unreal. I have seen some reviews of the new XPS 7590 with i7 9750H, it seems to have the same thermal throttling issues. Which means even tho it has an upgraded CPU it performs similarly to its predecessor with 8th gen Core i7 8750H.

The thermal and power limit throttle can make the laptop go as slow as 1GHz some cases.