Hi, you don't mention, or I do not understand what you are connecting to with the Horizon client, you only say "work related materials." If you are connecting to a Horizon desktop pool VM, it determines the number of supported monitors, although three can be supported, it is very typical that only two are, just depends how it was configured. Instead of All Monitors try Full Screen and see if it still freezes up (you will not get all three monitors though). The video cards on your local machine do not interact with the Horizon client performance.
Also what is utilizing the CPU? That could be a culprit as well.
