Xps 9500 and 5k

@ssc.schumacher  Please define "5K".  The traditional 5K resolution is 5120x2880, which that system won't run at all.  Then there's 5120x1440 "Dual QHD", for which Dell has this registry patch to make that resolution work on systems that use the Intel UHD 630 GPU, like the XPS 15 9500.  And then there's also 5120x2160 "UHD Ultrawide", which that system can't run.

Ok thanks. Will a Resolution of 3840x1600 work with the 9500? Is there a difference when  using a tb Dock?

@ssc.schumacher  3840x1600 should be completely fine since 4K is fine and that's an even higher resolution of 3840x2160.  I'm not sure what you mean about a difference using a TB dock.  Are you asking if there's a difference between using the display through a TB dock compared to connecting the display directly to the system?  If so, the answer is no.  If you want a Thunderbolt dock for an XPS 15 9500, the only real choice is the Dell WD19TB or WD19TBS.  The reason is that if your XPS 15 9500 has an NVIDIA GPU, then it will be designed for a 130W power source, and since 130W is above the 100W max of the USB PD spec, you won't find 130W support on third-party docks.  Dell only supports it on certain systems and certain docks, like the WD19TB/TBS.  The only difference between the TB and TBS is that the TBS dropped the 3.5 mm headset jack.  There's some shortage in the industry right now that affected production of those jacks or the audio chipset that runs them, so Dell created the "S" variants of their docks that didn't include that connector in order to prevent a huge dock order backlog from building up.  There's no other difference.