A Redditor has found that undervolting the GPU in the Dell XPS 15 7590 is necessary to prevent its throttling. The GTX 1650 in the latest XPS 15 is reported to throttle severely as soon as it hits 75 °C under load at the stock voltage of 800 mV. Lowering the maximum voltage to 700 mV was found to not only allow longer sustained performance but also lowered the operating voltage to 68 °C.
https://www.notebookcheck.net/Redditor-finds-a-solution-to-the-Dell-XPS-15-7590-s-GPU-throttling-issue.427893.0.html