Vostro 5402 compatibility with USB-C/DP docking station?

@Trufiadok  In order for a system model to be listed as "compatible" with Dell's WD19 docks, that system has to support all features of the dock, including the ones that require firmware support within the system, such as PXE boot, MAC address passthrough, and the ability to be controlled by the dock's Power button.  As of this writing, Dell doesn't implement support for those features in their Inspiron or Alienware lines at all, and yet owners of those systems are able to use Dell's WD19 docks with those systems just fine as long as they don't care about those particular features, even though no Inspiron or Alienware systems are listed on that sheet.  My wife uses a WD19 with her Lenovo laptop and the core features work just fine.

But in your case, given that Vostro 5490 and Vostro 5401 are both listed, I suspect the 5x02 models not being listed is simply an oversight despite how recently that document was updated.  I noticed a while ago that some XPS 13 models were incorrectly marked as requiring a WD19 180W when a WD19 130W was perfectly fine based on the power requirements of the XPS 13, and also that they incorrectly listed the XPS 15 9530 as compatible even though it didn't have USB-C/TB3 at all, while they did NOT list its successor the XPS 15 9550 that DID have USB-C/TB3.  I reported those errors to an internal Dell Support contact, who reported them to the Documentation team, and after several months the XPS 13 listings were corrected, and the 9530 was removed, but the 9550 was never added.  So unfortunately Dell's documentation isn't always perfect.

I would definitely choose a WD19 over a Dxxxx series dock, though.  The Dxxxx models use "indirect display" technology called DisplayLink -- not to be confused with DisplayPort -- and DisplayLink has some drawbacks that I wrote about in the post marked as the answer in this thread.