Thank you for joining the Graphics community.
Based on your description, yes, it seems related to the video adapter you are using. Regarding your questions, I would like to let you know Intel does not recommend video adapters, converters, splitters, hubs or docks since these can affect the resolution and quality that the graphics controller can provide; therefore, from my end there is no information on which adapter configuration will work. But, in case you have to use them I personally recommend the high quality and active units. It's possible that your computer manufacturer can provide a list of tested adapters for this specific model.
For more information on the resolution for this platform visit: Datasheet, Vol. 1: 7th Gen Intel® Core™ Processor U/Y-Platforms
Sort of, it passes the buck to ASUS in my case, since other users of the same adapter achieve 1440p that leaves ASUS. Thank you