P2720DC, XPS 13 9350, multiple issues

@Fenixman  I can offer a bit of clarity here -- as well as some hope!

First, the issue with the XPS 13 9350 not working with USB-C displays isn't related to daisy chaining, which involves running multiple external displays from a single PC output.  The issue occurs even when only trying to run a single external display, and it's some bizarre issue with the XPS 13 9350.  It also affects the XPS 15 9550 and Precision 5510, even though those aren't mentioned because that wasn't discovered until later and Dell evidently never bothered to update the KB article.  Dell has never been forthcoming about the underlying cause of the problem, but the bottom line is that the XPS 13 9350 does not send video when connected to Dell USB-C displays using a USB-C cable, even though the XPS 13 9350 works fine with other USB-C displays (and docks), and Dell USB-C displays work fine with other USB-C systems.

The USB-C to DisplayPort cable WILL work, however.  You don't have to worry about the lack of the DP logo because the XPS 13 9350 supports Thunderbolt 3, and video output over USB-C is mandatory for TB3 systems.  That's why Dell systems that support TB3 show the Thunderbolt logo instead of the DP logo.  And it has been confirmed that even on the XPS 13 9350 that can't send video over USB-C to Dell USB-C displays, connecting to that same display using a USB-C to DisplayPort cable does work.  The drawback is that in that situation, you're only sending video to the display over that cable.  You can't charge your system from the display anymore, nor do you have USB data connectivity if you want to use the USB ports built into the display.  And since the USB-C port on that display is the only way to draw power from it AND the only way to get USB connectivity between it and the system, I don't know of a way to use that port for both power and USB data but NOT video.  If you want to use it for USB data, you can use a USB-C to USB-A cable to connect the display to your XPS 13's USB port -- but then you'd have to power your XPS 13 using its regular power adapter.  If you want to use the display's USB-C port for power, you can get an adapter like this one.  You'd connect a USB-C cable from the display to the power input of this adapter, then connect a DisplayPort cable between the display and adapter as well.  That will cause your system's USB-C port to be used for video output and power input, but not USB data.  And again, since the P2720DC's only USB "upstream" port to connect to a PC is that USB-C port, that would leave your USB ports unusable, in which case you might just need to get a USB 3.0 hub instead.  I realize this is a huge inconvenience that totally defeats the point of having a USB-C display for single cable "docking station style" connectivity, but having to work around this compatibility issue between the XPS 13 9350 and Dell USB-C displays means the only solutions are a bit clunky and limited.

The issue with the DA200 is that it's limited to 1080p output.  This is stated in its documentation, available on support.dell.com.  It's not a problem with the device or anything related to the XPS 13 9350.  It's just a limitation of that particular device.  The newer DA300 when paired with that system will support up to 1440p 60 Hz or 4K 30 Hz.  (With newer systems it can run 4K 60 Hz.)  But the fact that you're limited to 1080p on the DA200 does NOT mean that you'll be limited to 1080p when using a USB-C to DisplayPort cable.