[NAME]  Running dual QHD 60 Hz from a DP 1.2 system requires a full interface worth of bandwidth. Your USB-C display is by default configuring the link to run both video and USB 3.x data simultaneously. Doing that cuts video bandwidth in half. Go into the settings of the first display in the chain and set its USB-C Prioritization setting to High Resolution instead of High Data Speed. In that setup, you’ll have full video bandwidth, but only USB 2.0 data speeds. Running dual QHD and USB 3.x simultaneously over a single cable requires DisplayPort 1.4/HBR3 (or Thunderbolt, but the displays don’t support that).
I have the Dell Latitude 5411 14’’ with Intel i7-10850H and Intel UHD 650 graphics. I have two Dell U2721DE QHD screens, which I connect via one USB-C cable. Windows gives me the option to either run one screen on 1440p 60hz and the other 1440p 60hz interlacing (which leads to dramatic stutter), or both at a maximum of a tiny bit above 1080p 60hz. Shouldn’t it be able to run two external QHD displays without issue? To my knowledge both display port 1.2 and the i7-10850H support this thanks in advance   
Dual Monitor 1440p support Latitude 5411