m16 R2, WD22TB4, external screens

External Screens on M16 R2 i9 

Hi peoples. I am currently running a Dell WD22TB4 dock with two 27" screens in addition to the laptop's screen. It seems that the external screens when run through the Thunderbolt port do not use the NVIDIA video card? But instead use the integrated video system. I read somewhere that only the internal screen and HDMI port is set to use the video card? Can anyone confirm that?

Also the main reason I am here is to see what external screen resolution the system will run, ie, will it run a 32:9 widescreen display? Looking at replacing the current setup with a single 49" widescreen but can not find anything anywhere on the max resolution. The screen I am looking at is just a cheap one, 32:9 1080. I am not using it for gaming etc, just an office PC that has bucket loads of tabs and windows running at once. But I don't want to buy it then find it won't work. Have google heaps but can't find anything!