The APEX2800 card is a hardware solution from Teradici that helps the pcoip_server_win32.exe process to encode the stream and thus reduce stress on cpu and memory. It does introduce a very tiny bit of latency, since the desktop protocol is sent through the card and then to the endpoint, instead of directly. The fact that you actually notice that lag is very dependant on the usecase. In some cases you notice nothing, in others you might annoy some endusers. Nvidia GRID is a solution that enables the VM's to use graphical acceleration by granting them access to the Nvidia GRID hardware trough use of a software layer, and giving the VM an actual graphics card in the device manager. New versions of the hardware actually assist the remoting protocol (Blast Extreme) with H.264 encoding, thus reducing latency instead of adding. This is dependant on your hardware and level of GRID software version.
A game is a very poor test for a VDI solution to be honest, especially since the behaviour of your applications can differ, even in the same session. Real world testing of your actual usecase is a better way to take a look at performance.