XPS 15 9570, with two 4K monitors

@malcolmgwood  yes you can run to 3 simultaneous independent displays, all of which can be up to 4K resolution.  However, you might not want to run the built-in display alongside dual external 4K displays.  The reason has to do with Windows display scaling.  A 15" 4K display is going to require a different scale factor than an external 4K display, and when you use multiple display scale factors simultaneously, Windows renders everything internally at the scale factor of whichever display was primary at the time the user logged in, and then uses post-render GPU scaling to shrink or expand the rendered image to achieve any other scale factors in use on other displays, similar to shrinking or expanding a JPEG photo.  As you might be able to guess, that technique doesn't look as good as Windows actually rendering for that other scale factor to begin with, especially with vector graphics like text.  So if you run this setup, just be aware that any displays running a scale factor different from your primary display will not look as good as they would if they were the primary display when you logged in.

Also sorry which Hub do I need to use? I have two 27in Dell 4k monitors and was thinking to buy the

Dell Performance Dock – WD19DC 240 watts or do I need the WD19TB?

Thank you

@malcolmgwood  you want the WD19TB, not DC.  The DC is meant for Dell laptops that require up to 210W of power, which it can deliver because it connects to TWO Thunderbolt ports on the system (DC = dual connector).  And although that dual head connector is magnetic so that it can be separated and support with systems that only have one port, in that setup it only works as a standard WD19, which won't support dual 4K displays.  (The reason for this is that the WD19DC is actually NOT a Thunderbolt dock.  It uses USB-C, but when it has two connectors active, it can run higher-end display setups typically only available via Thunderbolt.)  The WD19TB on the other hand will provide enough power for the XPS 15, connect using a single cable, and support dual 4K displays in that configuration because it uses Thunderbolt.

@malcolmgwood  if I understand your plan correctly, you want to connect the XPS 15 directly to a WD19TB dock, then connect the displays to that dock, and finally connect an eGPU to the "upstream" Thunderbolt port on the WD19TB?  I don't recommend that setup.

If you're using an eGPU, connect your external displays directly to the eGPU.  You'll take a performance hit if you use the eGPU to accelerate content on displays attached some other way, including the laptop's built-in display, since in that case the eGPU has to use PCIe (over Thunderbolt) to receive data from the system and then to use it again to send completed video BACK to the Intel GPU that's actually controlling the displays for final output.  And in the case of external displays, the Intel GPU would then have to use Thunderbolt a THIRD time to send that video out to your external displays attached to the dock.  That's a mess, and I think the performance hit of using an eGPU for indirectly attached displays is about 15-20% if memory serves, but I admittedly am not an expert on eGPUs.  By comparison, if the external displays are instead attached directly to the eGPU, then the eGPU can just pass the completed video straight out to them rather than consuming additional PCIe bandwidth.  That setup would also allow you to run technologies such as VR, adaptive V-Sync, and G-Sync (if you use an NVIDIA GPU), none of which would otherwise be possible because those technologies require that the dGPU have direct control of the display outputs that the displays are using.

And in fact if you're using an eGPU, you might want to consider getting the Razer Core X Chroma and then skipping the Dell dock entirely, because the Chroma version includes Ethernet and 4x USB ports, so that should get you everything you need unless a headphone/speaker jack is critically important to you.  In this setup with the eGPU enclosure connected directly to the system, you'd also have to connect the XPS 15's AC adapter directly to the system separately so that it has access to the full 130W it's designed for, but buying a dock just to avoid that additional cable connection seems like a very expensive proposition, and it comes with the performance tradeoffs I described.

Ok so I have connected my Razer Core to my WD19TB hub and it works perfectly. The problem now is that I have a TB3 NAS drive that I want to connect too but there is only one TB3 port on the WD19TB hub... what would be the best way to connect the NAS drive. Also there is a 10Gbe LAN port on the NAS drive but again I have my hub plugged directly into the router... How would I connect these two so I can benefit from the Speed of data transfer from NAS to XPS15? 

@malcolmgwood  I don't understand what you mean when you say you have a "TB3 NAS drive".  NAS stands for Network Attached Storage, which means that a NAS device would plug into a network jack (typically located on a router or switch) so that it becomes available to all devices on your network as a standalone device, without having to be "hosted" by some other device like a PC.  That's why NAS devices have Ethernet jacks.  So if you wanted to use your NAS device as an actual NAS, you would not plug it into a port on the dock that would cause it to operate as direct attached storage on your PC.

If you have some sort of device that supports operating as both direct attached storage and as a NAS, then are you certain that the direct storage port is actually TB3 rather than regular USB-C?  If it's just USB-C, then you can get a USB-C to USB-A cable and plug it into your dock that way.  If the NAS device really does have a TB3 port that you want to use and neither the Razer Core nor your NAS drive has an additional TB3 port to allow peripheral daisy chaining, then I think you're stuck.  I don't know of any Thunderbolt 3 "hubs", i.e. devices that will take a single TB3 port and give you multiple ports to plug peripherals into like USB hubs do.  Normally you either use a system that has multiple TB3 ports built in or you need to make sure that each TB3 peripheral you use has an "upstream" TB3 port so that you can keep chaining them along.

But what specific NAS device do you have?  I'm curious now.

Sorry yes I have Thunderbolt 3 NAS Drive with 2TB SSD and 8TB x 6 HDD RAID System. 

https://www.qnap.com/en/product/tvs-672xt/specs/hardware

Seem to be able to Daisy chain it so if I plug in the middle of the chain might work...? 

XPS to Hub > Hub to NAS TB3 > NAS TB3 to Razer Core / Razer Core to 2 x 4k Monitors

The other way I was thiniking was using the 10GBE LAN cable and getting that plugged into the Hub but not sure how to get LAN Internet as well at the same time...

@malcolmgwood  if your QNAP has a second TB3 port to allow daisy-chaining, then yes I would try putting the NAS between the dock and the Razer Core.  That's really the only available cabling option anyway.  The 10Gb Ethernet jack would be meant to be plugged into a network switch or something, not into a dock or directly into a system.  In theory, you could directly connect the NAS to a system if you knew how to configure static IP addresses, but 10Gb Ethernet wouldn't be as fast as TB3, and in fact the dock only supports Gigabit Ethernet anyway.  In addition, that would only get your NAS talking to your system.  The only way you'd be able to get the NAS visible to the rest of the network would be to set up some sort of network bridging between your laptop's Ethernet interface and its WiFi interface that you were using to connect your laptop to the rest of the network.  But at that point, your NAS only has WiFi connection speeds to the rest of the network, and it's only available on the network when your laptop is running in order to provide that bridging.  That's why NAS devices are instead normally connected directly to the network through a switch or router.

I'm guessing you're considering this because you want to keep your NAS near your dock so that it can be connected via TB3 but you don't have an Ethernet switch or router near your dock to plug the NAS's Ethernet interface into?  In that case, if you have coax cabling in your walls for cable TV and you have an outlet near your dock and another one near your router, you could look at something like a pair of MoCA adapters that essentially allow you to run Ethernet over that coax cabling.  That would get wired connectivity running between the NAS and your router.  It won't be as fast as native Ethernet, but it would be better than using your laptop to bridge your NAS onto the network via WiFi.  There's also powerline networking adapters that run Ethernet over electrical wiring, but those don't seem as reliable as MoCA.

Hi, just jumping on this thread. I'm confused. From my research I understand that the WD19TB would not work with an XPS 15 9750 if you had a 9570 that had a bigger batter. I didn't think the TB could provide enough power and you would have to plug in your external power supply. The DC I read gives you the full power needs?

@dr64  that is not correct.  Battery size has nothing to do with power requirements, just as having a larger fuel tank does not mean your car will get worse gas mileage (except to the extent that the additional fuel adds weight, but ignore that for the purposes of this analogy.)  There are some systems where different configurations will have different power requirements based on the type of CPU they were ordered with and whether they were ordered with a discrete GPU or only Intel Graphics, but the XPS 15 always uses a 130W power supply regardless of configuration, and the WD19TB can provide up to 130W to Dell systems, including the XPS 15.  The official USB Power Delivery spec maxes out at 100W, but Dell did something proprietary to stretch that to 130W, which they've also previously done on older docks like the WD15 and TB16.  The WD19DC can provide up to 210W, but that's because it has a dual USB-C connector, and it can only provide that extra wattage when actually used with a system that has two USB-C ports.  The XPS 15 9570 doesn't -- but again, it doesn't need that anyway.  With the regular WD19, you'd need to buy the version with a 180W power supply instead of a 130W power supply it can also be ordered with in order to be able to send 130W to the attached system, but the WD19TB comes standard with a 180W power supply.