We have not installed a ton of video walls but you seem to be aware of the different ways to do this. Using the graphic cards of a workstation and a VMS to that has a UI to drive cameras to these outputs is typically what we have done. Note that if you are trying to take a single graphics output and deliver it to multiple monitors then that brings it to the level of a real video wall in my definition (not just a wall with a bunch of displays). For that you will need a real video wall processor such as what is offered by RGB. Some display manufacturers have built in processors but I have found none of them maintain the native resolution of an image, for example of you had a 4K image being displayed through a graphics card that supported 4K, spreading that image across four monitors would not then provide you with a 4K image. Again, forces you to use a real video wall processor. I have never used the HikVision server with 6 HDMI outputs, don't know how they are accessed from a client, more familiar with Genetec. Genetec supports decoders but I wish someone made a high resoltuion decoder because if it was supproted you could drag and drop camera to said decoders, this is easier then using a workstation running the software to drive a display.