If Dell is not answering pre-sales questions then you don't want to experience aftersales support. In other words, ask them directly to check out how their phone support is today.
Does the 7590 with the 1660 Ti have the 144Hz display? It doesn't say it anywhere on the page for the specific one I'm looking at ($1200 variant with the 1660 Ti, 8 GB Ram, and i7-9750H). If this model doesn't have the 144Hz display, I might just go with the Helios 300. Thank you for any answers you give me!