For SW271C, SW321C, SW271, PD2720U, PD3220U model:
Apple M1 devices with Thunderbolt 3 connections to monitors may exhibit a resolution and refresh rate lock to 4K 30Hz. Make sure you have the latest MacOS version with all the newest updates to resolve this issue, which is caused by an out of date operating system version. If there's any further question concerning this issue, please contact BenQ Support.