Part number for WD19 dock TB module

You might have to call Dell Spare Parts about this.  I remember seeing the advertising about swappable modules, but I think that was geared more toward organizations that have dozens or hundreds of these rather than as an upgrade path for end users, so the module might not be advertised as a typical product.  However, be aware of a few things even if you can find it:

- The WD19TB is only sold with a 180W power supply, whereas the WD19 is sold with a 130W or 180W power supply.  So if you have the 130W version, I'm not sure the dock would function properly if you installed a WD19TB module.

- The WD19TB module is backward compatible with regular USB-C systems, so you could just permanently attach the WD19TB module and your USB-C system would still function with it.  However, when the module operates that way, it behaves equivalently to the regular WD19.

- If you're considering the Thunderbolt module because you're implementing a setup that will actually require Thunderbolt, then in most cases that won’t work so well for the regular USB-C system you're trying to use.  For example, if you'll be connecting dual 4K 60 Hz displays, then your Thunderbolt system will be fine with that, but a USB-C system wouldn’t be able to run that. You'd have to give up on some combination of resolution, refresh rate, and/or quantity of active displays when using that system.  The exact fallback possibilities would depend on whether the USB-C system supports DisplayPort HBR2 or HBR3 over USB-C.  The only use cases I can see where this issue wouldn't come into play would be if you a) want the Thunderbolt module in order to attach another Thunderbolt 3 peripheral to its "upstream" port and you only care about using that peripheral with your Thunderbolt system, or b) if your Thunderbolt system only supports DisplayPort HBR2 while your USB-C system supports DisplayPort HBR3, in which case moving to a Thunderbolt module would allow both of them to run certain setups, such dual QHD 60 Hz displays, for example.  An HBR2 system would need a Thunderbolt dock for that, while an HBR3 system could run that over a regular USB-C dock.

That's a change regarding the TB module being backwards compatible as if I plug the Latitude into my old TB15 dock then it says its not compatible.

The two screens are 2560x1440 so with USB-C I can only drive one at full resolution.

So the best bet might be to return the WD19 for a WD19TB?

@pwhatcher  interesting, I thought I remembered reading a note in the TB16's documentation indicating that its DisplayPort and Mini-DisplayPort outputs don't support DisplayPort MST (daisy chaining), so I'm surprised that setup is working for you, but my memory may be incorrect, or it wouldn't be the first time that documentation hasn't aligned with real world usage.

If you're already using the display's built-in USB hub with a third system, then I agree you'd be a bit stuck here.  The only way to have it all would be to add a KVM into the mix, but a triple source KVM that supported dual QHD displays is fairly expensive, in fact even a dual source KVM would be, and of course it's one more box to stash somewhere and a bunch more cables to deal with.  A friend of mine does have a setup like that though and loves it.  He's got a dock for his laptop plus a desktop system, both wired into the KVM, and then the USB peripherals like his keyboard and mouse that should be "switchable" between systems are plugged into the KVM, while the USB peripherals that should always be attached to a particular system are connected to the laptop dock or desktop PC.

@pwhatcher  one more thing: In terms of getting an HBR3 system, there are pretty much only two categories of systems that support DisplayPort HBR3 over USB-C right now:

• Systems with Intel "Ice Lake" CPUs, which are the Core 10th Gen CPUs that end with a "G" followed by a number.  They incorporate a newer "Gen 11" GPU that added HBR3 support.  The Core 10th Gen CPUs that end with a U or H are using an older architecture that still uses an older GPU that only supports DisplayPort HBR2. Intel somehow found a way to make their processor naming scheme even more confusing, and that is really saying something.  (And this by the way is why most systems even being sold today still only support HBR2.)
• Systems that have discrete GPUs that have direct control of the display outputs. These are fairly rare even among systems that have discrete GPUs, and when it comes specifically to Dell systems, to the best of my knowledge the USB-C/TB3 output is always controlled by the Intel GPU, even if the system might have one or more other display outputs that are directly controlled by the discrete GPU (such as certain gaming systems).  The only exception to this is Dell's Precision 7000 Series models from the 7x20 onward, which offer a BIOS option allowing you to choose which GPU controls the display outputs. They're able to do that because they use a more complex and expensive motherboard design.  But they also come with Thunderbolt 3 anyway.

Or if your employer gets you a system that supports Thunderbolt 3, you'd be good to go even if it was an HBR2 system.