Resolution and refresh rate compete for the capacity of a display connection. Increasing either generally increases the data that must reach the monitor. A connector that handles a high-resolution desktop at one refresh rate may not support the same image at twice that rate, especially when another screen shares the upstream connection.
Use a rough calculation to understand the pressure
An illustrative active-image estimate multiplies horizontal pixels by vertical pixels, frames per second and bits per pixel. For 1920 by 1080 at 60 frames per second with 24-bit RGB, that product is about 2.99 billion bits per second. Doubling the frame rate approximately doubles that active-image requirement. This explains the direction of the tradeoff without claiming an exact cable limit.
Actual transport needs more information than this simplified estimate. Timing intervals, link encoding and protocol overhead affect capacity, while chroma subsampling and compression can reduce the transmitted data in supported configurations. Do not compare the rough result directly with a headline connector speed and conclude the mode must work. The source, link and monitor must negotiate an actual supported format.
Two displays behind a shared dock or MST path can exceed a combined limit even when each works alone. The limiting resource may be the upstream link, available graphics streams or another host capability. Identify which resource the product's combined-mode table describes rather than assuming every failure is simply too many pixels.
Test a supported combination deliberately
Start with a documented mode on both screens and record resolution, refresh rate, color depth and HDR state where relevant. If a higher mode is advertised, change one setting at a time. A sudden loss of the second monitor after raising the first monitor's refresh rate is useful evidence about a shared constraint, not automatic proof of a defective panel.
Check the entire path. An older adapter or an inadequately specified cable can limit a connection whose endpoints support more. A port's version label alone may not establish every optional feature, including compression support. Use the exact model documentation for the combination rather than treating a version number as a promise of the maximum possible implementation.
Choose the tradeoff around the workload. Text editing may benefit more from readable resolution and stable scaling than an unnecessarily high refresh rate. Fast motion tasks may place greater value on refresh performance. A lower mode is not a universal recommendation; it is an option to evaluate against the task and supported hardware.
Keep the final verified combination in the setup record so later troubleshooting has a baseline. If a dock or cable changes, compare its complete mode support before expecting identical results. Understanding the bandwidth relationship helps explain why a configuration fails, while documented compatibility and controlled testing establish which arrangement is actually available on the particular system.