WD22TB4 for Non-Thunderbolt systems can only do 4k 30hz. you need a notebook with thunderbolt port to fully utilize this dock. You have over spent for this Latitude 5490.  If you are planning to use this notebook for long Get something simple like D6000 which will let you do 4k 60hz.    Alternatively you can use a type C to HDMI cable to get 4k 60hz., Since you only have 1 type C port you won't be able to use the dock. [URL]    
I have a setup with both a Latitude 5490 and the WD22TB4 dock. I'm trying to connect it to UltraSharp U2723QE monitor, but I can only get 4k30, not 4k60. I also have an old XPS 15 which can output 4k60 through the dock since it has a thunderbolt port, but I guess the Latitude doesn't. Is there any way to get 4k60 on my monitor through the dock?  
5490 + WD22TB4 = 4k30. Any way to get 4k60 (single external display)?