Seeking recommendations: dock

@Richmilnix  You're correct about the underlying cause.  The Targus dock you're using likely uses "indirect display" technology called DisplayLink (not to be confused with DisplayPort), and due to a Windows limitation, on systems that have multiple GPUs, only the primary GPU can be used to accelerate content on DisplayLink-attached displays -- and on systems with Intel and NVIDIA GPUs, the Intel GPU is primary.

In terms of alternatives, you'd want a USB-C dock that tapped into a native GPU output wired to the system's USB-C port.  This capability is called DisplayPort Alt Mode, but it is an optional capability on USB-C ports and not implemented on all systems that have such ports.  Looking at the Setup and Specifications document for the Inspiron 7778 here, it's not entirely clear whether that system's USB-C port has this capability.  There's a paragraph describing USB-C ports in general that mentions it can be used for external displays, but afterward it only mentions support for USB 3.1 Gen 1 (5 Gbps) and Power Delivery.  Unfortunately, sometimes Dell documentation has general descriptions of port capabilities even if some of those capabilities aren't implemented on that particular system.

If you can find confirmation that your USB-C port supports video output, then a dock like the WD19 would work fine.  I don't know if your system supports being charged through its USB-C (another optional capability), but if it does, then the WD19 can provide up to 90W, and the specs of that system indicate that it only needs 65W.

If you want to test video output support, you can get a USB-C to DisplayPort or USB-C to HDMI dongle/cable and see if you get video output when you connect a display to it.  Or you could just buy the dock and return it if it doesn't work out.  But if it does work, be aware that the Inspiron 7778 is a DisplayPort HBR2 system, which means that when used with a USB-C dock like the WD19, you can run dual displays up to 1920x1200 each or a single display at 2560x1600 (or a single 4K display but only at 30 Hz rather than the standard 60 Hz.)  Hopefully your display setup isn't higher end than that.

If your USB-C port doesn't support video output, or your display setup exceeds the capabilities of the GPU output wired to your USB-C port, then unfortunately you don't have any great options for a docking station.  You'd have to connect your display directly to the system's HDMI output.

Hopefully this helps!

@jphughan Hi There, appreciate your advice provided throughout a number of available threads here.
I too have a similar question re; what would be the best dock to utilise that will allow best gaming graphics?

Set-up per below:
Dell G7 7590
Thunderbolt 3/DisplayPort (Only on computers shipped with graphics card NVIDIA GeForce RTX 2060, RTX 2070 Max-Q, or RTX 2080 Max-Q)- I am a RTX2060.

Screens in question: 
2x Dell U2719DC 2560X1440 @ 60 hz

I am trying to establish what dock would facilitate me running both screens via the one plug (I anticipate this will be the Thunderbolt 3) at their 2560X1440 @ 60hz resolution and refresh rate.

The Dell TB16 sounds like a likely option, unless there is another model that avoids DisplayLink that would be suitable?
Charging via the Thunderbolt 3 is irrelevant, as the G7 7590 does not support this, I am told.

Looking at the NVIDIA control panel configuration (per one of your other posts) it has both the monitors linked to the Intel UHD 630, when they are connected at current in a daisy-chain (Thunderbolt to Monitor 1, and Monitor 1 DP to Monitor 2 DP) if this helps inform your recommendation.

Appreciate your thoughts.

Hey @Cal740 , the TB16 was replaced a while ago with the WD19TB, and since the TB16 generated more than its fair share of complaints while the WD19TB doesn't seem to be, I would recommend going with the WD19TB instead.  In terms of functionality, it's possible that the system's built-in Mini-DisplayPort output is wired directly to the NVIDIA GPU (you can test this if you have a way to connect a display to that output), in which case if you had displays that supported G-Sync, there would be a benefit to connecting the displays directly to the system rather than through a dock that relied on a display output controlled by the Intel GPU.  But that of course means bypassing the dock for your displays, and if you're using U2719DC displays, which don't support G-Sync, then connecting directly to an NVIDIA-driven output is less of a benefit.  (Although you'd still likely be able to use Adaptive V-Sync with the U2719DC if you were to connect them directly to an NVIDIA-driven output, which wouldn't be the case when going through an Intel GPU, if that feature is important to you.)

In any case, if you want to be able to run dual QHD displays from that system through a dock, yes you would need a Thunderbolt 3 dock.  However, as you say you won't get the benefit of being able to charge the system from the WD19TB, and to my knowledge Inspiron G Series systems don't have firmware-level support for "bonus" features of Dell docks like being able to use the dock's Power button to control the system.  So you may want to look into third party options that might cost less.  CalDigit has the TS3+ and USB-C Pro Dock models, for example.  The latter despite its name will take advantage of Thunderbolt capabilities if the attached system supports it, but it's also backward compatible at reduced functionality with non-Thunderbolt systems, which isn't true of the TS3+.  But the TS3+ has more port options overall.  And either one of them will run up to dual 4K 60 Hz displays via native GPU outputs.  Hopefully this helps!